Bulgaria's ambassador to the UK has called Nigel Farage's arguments against lifting migrant restrictions "very feeble".
Konstantin Dimitrov was referring to leaflets sent out by Ukip ahead of the council elections in May describing Bulgarian people as a "threat" to Britain.
The material, which the ambassador referred to as "hostile propaganda", questions the impact of immigration from Bulgaria and Romania on local services and employment.
Earlier this year Farage said: "We have nothing against people from Bulgaria and Romania, we wish them well, but we do not think it's right this country has a total open door policy."
Speaking on the Sky News Murnaghan programme on Sunday, Dimitrov said: "It is not the reflection of the prevailing mood of the British people towards the Bulgarian people but it is very disappointing and very discriminatory in certain aspects.
"We react firmly, politely, but very strongly against these assertions and the atmosphere created by this propaganda.
"There were, for instance, pre-election leaflets in counties that say the Bulgarians will be a threat to social system of the UK. This is absolutely unacceptable in a European country."
When asked if he had put these concerns to Farage himself he said: "He is usually very feeble in presenting solid arguments to put it mildly and prefers to indulge in propaganda which deviates markedly from the essence of the debate."
Restrictions on what jobs Bulgarians and Romanians can do in the UK expire in 2014 leading some to fear an influx of economic migrants.
Ukip insist they are voicing the concerns of many British residents.
Farage said the pressure on housing, education and services from immigration "poses a major problem" especially if people from other countries claim benefits.
Speaking earlier on the same programme, Labour MP Diane Abbott warned politicians - including her own leader Ed Miliband - had to be careful to avoid "dog whistle politics" on immigration.
She said: "We are in the middle of a recession, or as near as damn it. In a recession you always see a rise in racism and anti-immigrant feeling - you had it in Germany in the 1930s.
"We have to be very careful about our language because when people are frightened about their future, they want to blame outsiders, they want to blame the other.
"I know Ed thinks very carefully about what he says on the question, there is nothing he has said I disagree with.
"But I think all parties need to be careful of dog whistle politics on immigration where the text is fine but the underlying message is one that maybe is not so fine."
Faith minister Sayeeda Warsi earlier told Murnaghan that David Cameron had made great strides in taking racism out of the immigration debate.
She said: "Politicians are regularly looking for those which can unite us - we talk about values, sometimes we talk about symbols like the Union Flag.
"We have to keep focussing on those things that unite us. Of course there has to be some quite targeted work... but I think we have got to come back to the approach this Government has adopted, which is about focusing on those things that unite us, being very strong against issues of discrimination and protecting those communities who feel they're subjected to hate crime.
"One of the things David Cameron did incredibly well, even in opposition, was to de-racialise the immigration debate. Immigration is not about the colour of anyone's skin any more, it's a simple issue of resources at any one time."