David Cameron is under pressure to pull out of an alliance with a right-wing Polish party because they have become too extreme.
Tory MEPs formed the European Conservatives and Reformists, with Poland's Law and Justice party.
But the Polish group's leader Michal Kaminski, who has himself been accused of homophobia and failing to commemorate the Holocaust, has quit, saying his colleagues are too far right for him.
Resigning last week, he said: "My party is being taken over by the far right." It is embarrassing for the Prime Minister and Foreign Secretary William Hague, who hailed them as moderates.
Labour MP Denis MacShane said: "Now that even Michal Kaminski cannot stomach his own party it is time for David Cameron to pull the plug on this foray into the extremist swamps of East European hard right political parties."
The Euro alliance said it was an "internal matter".
Daily Mirror
