Foreign Secretary David Miliband and his shadow William Hague have traded accusations over statements made by Polish MEP Michal Kaminski regarding a massacre of Jews in Poland in 1941.
The row was sparked by comments by the MEP, who leads the group in the European parliament the Conservative party are members of, that it was "unfair" to compare the massacre at Jedwabne with "Nazi crimes".
"You can't go around hair splitting when it comes to murdering people on the basis of their religion," Mr Miliband said.
But Mr Hague suggested that many of the parties in the Socialist group of which Labour are members have views Mr Miliband would be uncomfortable with, including holocaust denial and homophobia.
"To damage relations with friendly countries in pursuit of a partisan agenda in British politics is not in keeping with the office of British foreign secretary," he said.