Disclosure by Bush 2004 campaign manager is met with criticism over party's hostility towards gay and lesbian rights

One of the key architects of the Bush-era Republican election machine that exploited anti-gay prejudices to motivate its conservative base has disclosed that he is gay and is lobbying to legalise same-sex marriage.

"It's taken me 43 years to get comfortable with this part of my life," said Ken Mehlman, a former chairman of the Republican national committee and the manager of George Bush's 2004 presidential campaign, in an interview published on the Atlantic's website.

Mehlman's revelation makes him the most senior figure in the Republican party to publicly identify himself as gay. As a member of Bush's inner circle, Mehlman would have been party to the agenda of hostility towards gay and lesbian rights that the Republicans adopted. It was designed to draw conservative and religious supporters out to vote.

Mehlman said he was aware that Karl Rove, Bush's chief political adviser, worked to place anti-gay initiatives and referendums on election ballots in 2004 and 2006 to help the party, a claim Rove has hotly denied.

While Mehlman expressed his regret at Republican tactics during his tenure, some gay activists were angry with him. Mike Rogers, who attempted to out Mehlman and a number of other politicians, wrote on his blog that Bush's 2004 election campaign was "the most homophobic national campaign in history. That campaign was run by one of the nation's worst closested individuals, Ken Mehlman."

Rogers said he wanted to hear Mehlman apologise for the damage he helped cause. "Ken Mehlman is horribly homophobic and no matter how orchestrated his coming out is, our community should hold him accountable for his past," he said.

Other critics pointed to recent political donations by Mehlman to Republicans opposed to gay marriage or to revoking the "don't ask, don't tell" policy barring homosexuals serving in the US military. In 2010, Mehlman's donations include $2,000 to the conservative Idaho senator Mike Crapo, who voted for a constitutional amendment banning gay marriage.

"Mehlman is following the same line he touted in 2004 and 2006 as a major Republican party power leader: support anti-gay politicians who are all too comfortable demonising [lesbian, gay, bisexual and transgender] people for some votes," said Michael Jones, of change.org.

Others welcomed Mehlman's declaration that he was taking an active role in the American Foundation for Equal Rights, the group behind challenges to California's Proposition 8 banning same-sex marriage. Chad Griffin, an activist against Proposition 8, said Mehlman had made a great contribution. "When we achieve equality, he will be one of the people to thank for it," Griffin told the Atlantic.

Liz Mair, a Republican blogger and consultant, said: "Ken Mehlman single-handedly has probably helped move the country, and the Republican party, in a more gay-friendly and equality-minded direction."

There has been no response so far from Bush, who was informed by Mehlman several weeks ago.