Tory Alan Duncan has said he is prepared to work for the Democrat campaign of John Kerry to prevent a second Bush term in the White House.
Mr Kerry has at least two supporters in the Parliamentary Tory party
The constitutional affairs spokesman says he is an "instinctive Republican" but is concerned at the influence of Neo-Conservatives in Washington.
He told BBC News Online: "I find myself more at home with Colin Powell than with Donald Rumsfeld."
Mr Duncan first met Mr Kerry in 1982 when the MP was at Harvard.
Traditionally Conservatives in the UK have been more closely identified with Republicans in the US than Democrats, who have had closer links with Labour.
Mr Duncan met Mr Kerry again last year when he was Tory foreign affairs spokesman.
His last foray into domestic US politics was when he attended the Republican convention that selected Bob Dole as their candidate for the 1996 White House elections - a contest won by Bill Clinton.
In a separate interview, Mr Duncan told the Times: "I intend to go over there in the next couple of months.
"It's partly about making links, but I will also help if I can. I want John Kerry to win."
More dangerous world?
Mr Duncan has said he feels that Neo-Conservatives such as defense secretary Mr Rumsfeld are making the world a "more dangerous place" because of the way they are dealing with the threat from international terrorism.
Meanwhile another Tory MP, Simon Burns, said he too supported Mr Kerry's bid to win power.
"I am probably a bit of an aberration in the Conservative Party in that I have always identified with the Democrats, but there may be a shift of emphasis going on in our attitude to the current administration," he told the Times.
"I cannot believe myself and Alan are the only Tory MPs who vote against Bush if we had the chance."
The US presidential elections are due to be held on 2 November 2004.