UKIP campaigns for the UK to withdraw from the European Union
UK Independence Party MEP Nigel Farage has defended calling Belgium "a non-country", saying it is "an artificial construction" which is "breaking up".
Appearing on the BBC's Question Time, he said he did not regret his comments and felt they were "very moderate".
The Euro MP also defended disparaging remarks he made to the EU President Herman Van Rompuy.
Welsh Secretary Peter Hain, who also appeared on Question Time, said the outburst was "beneath contempt".
Mr Farage is the former leader of the UK Independence Party, but stood down in September 2009 to focus on trying to win a UKIP seat in Westminster.
He plans to challenge Tory MP and Commons Speaker Jon Bercow in his Buckingham constituency.
'Not a diplomat'
Mr Farage drew jeers on Wednesday when he told the chamber of the European Parliament that Mr Van Rompuy had "the charisma of a damp rag" and the appearance of a "low-grade bank clerk".
He accused Mr Van Rompuy, who was in the chamber, of having "a loathing for the very concept of the existence of nation states", adding: "Perhaps that's because you come from Belgium, which is pretty much a non-country."
On Thursday, Mr Farage, whose party wants the UK to withdraw from the EU, told Question Time he had no regrets: "If I'd been summoned as a diplomat working for the Foreign Office then clearly one wouldn't have made comments like that.
"But I'd been summoned as one of 72 MEPs from the UK to something that calls itself a Parliament, but actually, it isn't a Parliament because it doesn't believe that any voice of opposition should exist whatsoever."
Mr Farage defended his remarks about Belgium by claiming that divisions between its two major linguistic and regional groups, the Flemish and the Walloons, would soon lead to a permanent split in the country.
"The country was an artificial construction and we're now at a point where the Flems and the Walloons are barely on speaking terms.
"Belgium is a prototype for the entire European Union. Belgium is going to split, it'll do it within the next few years... and when you criticise Belgium, you criticise the flawed European Union model, and that's why they're really upset with me."
Accused by fellow panellist Janet Street-Porter of being racist, Mr Farage replied: "Racist towards who? The Flems or the Walloons?"
Herman van Rompuy is sometimes described as "the grey mouse"
Mr Hain was one of several politicians also to condemn the comments.
Shadow defence secretary Liam Fox said: "I think it was frankly insulting... the sort of caricature and cartoonish approach of UKIP is not acceptable in this country."
Mr Farage has been summoned by the head of the European Parliament, Jerzy Buzek, to a meeting next Tuesday and is likely to face some form of reprimand, possibly a suspension.
Mr Buzek is said to consider Mr Farage's outburst to have been "completely undignified", while Mr Van Rompuy said he held the comments "in contempt".
Meanwhile, the BBC has announced that Question Time will feature an all-female audience next month for the first time in its 30-year history.
The special programme, to be filmed in Dewsbury, West Yorkshire, is timed to coincide with International Women's Week.