Shadow Conservative environment secretary Nick Herbert has accused Labour and the Lib Dems of having equally unsavoury allies in Europe.
His party has been attacked in the past 12 months for breaking away from its former allies to honour an promise made by Tory leader David Cameron.
One party in the group, the Polish Law and Justice Party, has been accused of homophobia, racism and anti-Semitism.
Mr Cameron has consistently said that the Polish party are not homophobic, although Mr Herbert did not defend it.
Instead, he wrote on Guardian.co.uk: “If [Denis] MacShane and others (Nick Clegg tried the same line in the second TV debate) want to attack us for the views of some members of political parties in eastern Europe, they’ll find we can play the same game.
“Labour is allied with parties who have banned gay pride and called homosexuality a disease; the Liberal Democrats with a party that called it a mental disability.”
He is thought to have been referring to Labour’s Bulgarian and Lithuanian allies, and to the Lib Dems’ Latvian and Lithuanian allies.
He continued: “If we conduct the debate to such pitiful standards, these political links would be sufficient evidence for us to brand Labour and the Liberal Democrats extremists, holding views by association which are beyond the pale.
“We don’t make this logical leap because it’s patently absurd. Neither should our opponents.”
He added: “Whatever the result of the election next Thursday, the Commons will look very different.
“It will be younger, more representative and more socially liberal. It will naturally want to entrench and advance equality for gay people which, to their credit, the Labour government can claim as one of their achievements.”
This week, the Conservative Party suspended a Scottish candidate for writing on his website that homosexuality was not normal.
This was the third embarrassment for the party during the election campaign, as last month, shadow home secretary Chris Grayling was recorded saying he agreed bed and breakfast owners should have the right to bar gay couples if they wish.
He later apologised and said he believed it would be “wrong” for gay couples to be turned away from businesses.
Meanwhile, PinkNews.co.uk revealed last week that Julian Lewis, the incumbent MP for New Forest East and shadow defence minister, told a constituent that he was against equalising the age of consent for gay men as he believes gay sex carries a high risk of AIDS.
A PinkNews.co.uk poll carried out last week suggested that support for the Conservatives among the LGBT community had dropped in the last year.
It found 58 per cent of almost 1,000 LGBT voters said they intend to vote Liberal Democrat next week, compared with 21 per cent for Labour and just nine per cent for the Tories.