A letter signed by celebrities including Ewan MacGregor, Stephen Fry and Jo Brand has asked Tory leader David Cameron to oppose the views of his party’s new European allies.

Fry tonight told Channel 4 News that Mr Cameron had aligned his party with an “unpleasantly homophobic nationalistic party in Poland and [is] sharing their whip in Europe.

Cameron broke away from an alliance with the EPP in Europe to honour an election promise he made but his new allies have been accused of homophobia, racism and anti-semitism.

The party has invited Polish Law and Justice Party MP Michal Kaminski, to speak at its conference this week. Kaminski was filmed calling gay people “fags” in an interview in 2000. He is now the president of the Tories’ new bloc in Europe, the European Conservatives and Reformists Group.

The Conservative Party is due to host a special gay event tonight in Manchester called Conference Pride.

The letter said: “It is not just that your new Polish allies oppose gay marriage and adoption but that their vile rhetoric – branding homosexuality as a ‘pathology’, gays as ‘perverts’, and describing ‘the affirmation of homosexuality’ as ‘the downfall of civilisation’ – was used to whip up hate during their election campaign.

“Your party’s decision to host an LGBT event at conference is a good step in the right direction.

“But it will seem empty – a two faced gesture – if in the same week you fawn over allies whose homophobia has no place in modern Manchester, in modern Britain, or in Europe.”

It added: “We want to believe the Conservative Party has really changed – please help us by rescinding the invite to the Polish Law and Justice Party and urging them either to change their views or quit your new European group.”

In an interview to be broadcast tonight on Channel 4 News, Stephen Fry said: “This is a problem that is not going to get smaller because, as we start to pay for the financial disaster of the last year, a kind of great pimple of nationalism, homophobia and racism is going to erupt around Europe because there is going to be trouble with unemployment.

“The problem with the 30s was not that period. It was the end of the 30s when you start to pay the price – and that’s why it matters now to make a stand because things will get worse.

“I, like many others, fully believe the Tory party has changed its rather antagonistic stance towards gay and lesbian people and that the days of clause 28 and section 28 are well past us.

“It upset me to see the Tories for strategic reasons sitting with an unpleasantly homophobic nationalistic party in Poland and sharing their whip in Europe.

“While it may not seem important as to whom they sit with, to me it just struck a very sour note and I just thought it would be very good during the conference to give David Cameron and the Tories an opportunity to disassociate themselves from that kind of 20th century, or frankly 19th century, rhetoric that the Polish Law and Justice party has been responsible for.

“It seems extraordinary that the modern Tory party, in which I fully believe in terms of its acceptance of gay people, should suddenly have changed its tune or at least allow itself to associate itself with these people.”

But Conservative MEP Charles Tannock told Channel 4 News “It’s very clear that the modern Conservative party is fully committed to equal opportunities to tolerance and anti-discrimination measures.

“I’ve been a member of the European parliament for tenyears, I’ve known the Polish Law and Justice party for five years, I know central and eastern Europe extremely well, and I have never come across any utterances of the kind that Stephen makes strong allegations about.

“I would also argue that Poland is a deeply conservative Catholic country, a bit like Britain 50 years ago, and one of the roles we can play is to move the public opinion in Poland in the right direction.

“I think our influence in central Europe with this new group will mean that our kind of tolerant vision of Britain and the rest of Europe will carry much more weight if these people are people we have communication with.”