
Nigel Ace, from Swansea, was part of a two-man demonstration staged by campaign group Fathers 4 Justice at the property in Herne Hill yesterday.
Sales manager Mr Ace, aged 40, now lives in North Somerset, but was born in Gower and has a primary school age daughter, who still lives with her mother near Swansea.
Mr Ace, who took to the roof dressed as Spiderman, said he and his fellow protester, 42-year-old Tony Ashby from Leicester, who was dressed as Batman, were staging the protest following Ms Harman's recent promises over equality in the workforce.
Mr Ace said: "What about dads? We haven't got equality.
"The government is ignoring us and has a feminist agenda.
"We want Harriet Harman to come back here and engage in a debate with us and, if not, Gordon Brown should come.
"I am trained in survival, so I don't care how long we are up here."
It is the second protest at Ms Harman's south London home by members of Fathers 4 Justice in just over a month.
Officers from Scotland Yard were called to the home of the Minster for Women at 6.20am yesterday, where Mr Ace and Mr Ashby unfurled a banner on the roof declaring "Stop the war on dads".
The pair are said to have at least three days' supply of food and water.
According to Fathers 4 Justice, Mr Ace had regular contact with his daughter following the breakdown of his marriage until his former wife withdrew access, leading to a battle in the family courts which has lasted two-and-a-half years.
They say two expert reports concluded he was a loving father who posed no risk to his daughter, and that Mr Ace and his elderly parents just want to play a meaningful role in his daughter's life.
A spokesman for Fathers 4 Justice said: "In the way women campaigned for equal rights in the workplace, we want equal rights in the home and to our children.
"Our government and Harriet Harman are legally, morally obliged to deliver."
Two men who staged a similar protest on Ms Harman's home last month were arrested on suspicion of criminal damage and causing a public nuisance, and were bailed by police until July 16 pending further inquiries.
The two men said they will not come down until the Government "takes them seriously".
The men said their names were Nigel Ace, 40, who was dressed as Spider-Man, and Tony Ashby, 42, in the Batman costume. They said they had enough food supplies to last for a week.

Mr Ace, who described himself as a sales manager from Bristol, said the stunt was provoked by Ms Harman's recent pledge to ensure equality in the workforce.
He said: "What about dads? We haven't got equality. The Government is ignoring us and has a feminist agenda. We want Harriet Harman to come back here and engage in a debate with us and, if not, then Gordon Brown should come. I am trained in survival, so I don't care how long we are up here."
Mr Ashby, who described himself as a painter and decorator from Leicester, said he had not seen his children for seven years.
He said: "We have been up here since 6am and we are in for the long haul. We don't want to cause trouble, we just want to get our message across."
The protest comes as Ms Harman is due to stand in for Gordon Brown in Prime Minister's Questions in the Commons while he attends the G8 summit in Japan. She left her home in Herne Hill, south London, at 7.45am and ignored the protesters, who draped a flag on her wall saying "Stop the war on dads".
The men said they had not been involved in any previous stunts and drew straws to decide who would stage the protest.
The demonstration is the second time in little over a month that Fathers 4 Justice has staged a protest at Ms Harman's home.
DEDICATED TO OUR DARLING HARRIET!!!
SEE LETTER OF PROOF. NO ONE BELIEVES YOU!!!
Around 30 banner-waving protesters dressed as various superheroes stopped at the courts during a street demonstration through Bristol in support of fathers' rights.
Around 10 protesters dressed as Spiderman, Batman, Superman and The Incredibles forced their way into the court and chanted "What do we want? Justice. When do we want it? Now."
A fire alarm was activated, although court staff could not confirm who was responsible, and nearly 100 staff flooded into the street outside.
Two police vans arrived, along with two fire engines, and the men soon left the court building and continued their march.
The demonstration was joined by two campaigners who scaled the roof of deputy Labour leader Harriet Harman's home in Herne Hill, south London, earlier this week.
Jolly Stanesby and Mark Harris, both from south Devon, started the rooftop protest on Sunday and continued for more than 24 hours. They have since been bailed by police.
Mr Stanesby, from Ivybridge, said: "We always have a little get-together before Father's Day to put our message across."
Fathers 4 Justice is a civil rights group which campaigns for parental equality and a father's right to see his children.
Mr Stanesby added: "Just because my ex decided to move on to another boyfriend shouldn't mean I don't get to see my child.
"Her new boyfriend can see my child as long as he likes, whereas I have to apply and have boundaries. I have to have checks, doctor reports... The courts are corrupt."
Mr Stanesby said he and Mr Harris have written to Ms Harman to request a meeting with her.
He said: "She's Minister for Justice and Minister for Women - how can those two things go together?"
Mr Harris, from Plymouth, said opening family courts to the public was one of the focal points of the Fathers 4 Justice campaign.
He said: "Open up the courts so people can see the ridiculous decision made against fathers. I was once sent to prison for waving at my daughters."
The march started at The Pithay and moved up to Perry Road via Corn Street and Colston Avenue, where the group unveiled a new poster campaign.
The poster showed an image of a child dressed in a superhero costume and read: "If this little superhero doesn't see his daddy on Father's Day, he doesn't see half his family."

Fathers 4 Justice group in 'graffiti' paint stunt besides M5 at Burnham
Controversial campaign group Fathers 4 Justice has carried out two 'graffiti' paint stunts on land besides the M5 motorway in Burnham-On-Sea this week.
The high-profile group, which is renowned for its publicity-seeking tactics, has spray-painted its name over two sets of farmyard silage bags at two sites north and south of junction 22 of the M5 motorway at Burnham, as pictured here.
Sedgemoor District Council has strict rules on advertising hoardings next to roads, but it says that its regulations do not cover this type of 'graffiti' - even though it is so highly visible to motorists.
Spokeswoman Claire Faun told Burnham-On-Sea.com: "It's difficult for us to act as Fathers 4 Justice appears to have done this without the consent of the landowner."
"We can only take action where landowners have breached planning conditions by taking money and given their consent to advertising hoardings being located on their land. In this case, this appears to be graffiti."
A surprised spokeswoman for land owner Bill Hancock, whose land is at one of the two sites, said she was unaware of the attack when Burnham-On-Sea.com contacted her this week.
"We didn't know this had happened and are naturally very unhappy about it," she said.
Once a mental hospital, the grade II listed house, which is 400 years old, has been converted into luxury apartments.
F4J bosses have said the stunt was carried out by a guerrilla splinter group following plans to step up operations in the city. Matt O’Connor, who founded F4J in December 2002, said he was not aware of the stunt.
He said: “There’s a lot of random activity going on in the West Country at the moment. This has been carried out by a guerrilla faction of Fathers4Justice. That’s the nature of our campaign at the moment.
“There’s always been a very strong power base in Bristol and things are starting to heat up again.”
Mr O’Connor has referred to Bristol as the “engine room” of Fathers4Justice in the past.
But the move has been branded "inappropriate and irresponsible" by the judicial office.
Nationally, the group has drawn up a list of judges who, it claims, have treated dads badly during family law cases.
Their names and addresses have been published on the F4J website, www.fathers-4-justice.org, in a list headed "Your Time Is Up: Britain's Worst Judicial Offenders".
Five judges from the Bristol circuit are named on the list: Andrew Rutherford, Paul Robert Barclay, Richard Bromilow, David Keith Ticehurst and Susan Darwall Smith.
The campaign group is planning to target them with direct action during the coming weeks.
F4J's Bristol co-ordinator, Nigel Ace, said: "We will be targeting judges nationwide and are going to be doing a lot more of these kind of stunts to put the wind up them. There are going to be more rooftop protests.
"There has been too much talking, what with everything that's happened since the original group disbanded. We're now going back to our older tactics."
Mr Ace said the judges being targeted were ones who are known to the campaign group through members who have tried to get access to their children in the city.
He said: "We're all for equality - but there's no equality in the family courts.
"You go in and feel like you're a child, but worse, because you're so powerless."
The announcement comes days after the campaign group launched itself in America.
Campaigners dressed as Captain America and Batman climbed on to the Lincoln Memorial in Washington DC.
Mr Ace hinted that the group could carry out more direct action in Bristol soon.
A Judicial Communications Office spokesperson said: "There is no justification or public interest served in publishing the home addresses or other private details of judges.
"It can serve no purpose other than to intrude into the privacy of the judge and encourage harassment of the judge and his/her family in their home.
"In the case of their court work, family judges have to make difficult decisions based on the individual circumstances of a case.
"By their very nature, these cases are emotional and feelings often run high.
"However, all parties have the opportunity to express their opinion to the judge prior to a decision being made and the right to seek to appeal decisions that they regard as unfair."