The Bulgarian ambassador to the UK called the tone of the immigration debate "very unpleasant".
Konstantin Dimitrov told ITV News Political Correspondent Carl Dinnen, "It is defamatory, definitely there are elements of discrimination."
"This propaganda hurts the pride of many Bulgarians ... the humiliation that such a rhetoric contains is something that may leave a trace here or there in the soul of my compatriots," he added.
The immigration debate is underway in earnest in the Commons, exposing the rift which cuts through the Conservative Party in Westminster.
The Immigration Bill was shunted into the sidings over Christmas while ministers worked out how to head off a rebellion they saw coming.