David Cameron was facing mounting pressure to condemn a Tory MP who branded the Olympic opening ceremony "leftie multicultural crap" on Saturday.
Aidan Burley, who was forced to quit as a ministerial aide after attending a Nazi-themed stag do last year, delivered the barb on Twitter during the event last night.
One post read: "The most leftie opening ceremony I have ever seen - more than Beijing, the capital of a communist state! Welfare tribute next?"
Shortly afterwards he added: "Thank God the athletes have arrived! Now we can move on from leftie multi-cultural crap. Bring back red arrows (sic), Shakespeare and the Stones!"
London Mayor Boris Johnson added his voice to a barrage of criticism, dismissing the comments as "nonsense".
Visiting the Olympic Park on the first day of the Games, the Conservative politician said: "It was actually the truth about this country in the last two or three hundred years told in a big, dynamic way.
"People say it was all leftie stuff. That is nonsense. I'm a Conservative and I had hot tears of patriotic pride from the beginning. I was blubbing like Andy Murray."
Another Tory MP, Gavin Barwell wrote on Twitter: "@AidanBurleyMP with respect, us Londoners are rather proud of the diversity of our city #nothingleftwingaboutit."
Downing Street moved quickly to distance Mr Cameron from the comments, with a senior source saying simply: "We do not agree with him."
But Mr Burley struck a defiant tone in interviews, insisting he still thought the event had been "trite".
"I wasn't having a go at multiculturalism itself, I was having a go at the rather trite way, frankly, it was represented in the opening ceremony," he told the BBC.
He admitted his tweets might not help his career but said he welcomed the debate.
"We all love the NHS but really for all the people watching overseas, 20 minutes of children and nurses jumping on beds, that seems quite strange," the MP added.
"And then we had all these rappers - that is what got me to the point about multiculturalism."
Labour frontbencher Michael Dugher said: "David Cameron should show some leadership and demand a full apology from Aidan Burley immediately.
"Burley has got form. His comments were stupid, ignorant and offensive.
"David Cameron has said that the Conservative Party has changed but it is clear from the words of his own MP that not a lot has changed."
Mr Burley was touted as a Tory rising star when he won Cannock Chase seat in 2010 with a huge swing from Labour.
However, he lost his job as a parliamentary private secretary when details emerged of a stag do he attended in the skiing resort of Val Thorens last December.
One guest was alleged to have dressed in an SS uniform while others were said to have chanted Nazi slogans.
Mr Burley, who is being investigated by French police over the incident, has repeatedly apologised for being present at the event but denied behaving badly himself or breaking the law.
"Seems my tweet has been misunderstood. I was talking about the way it was handled in the show, not multiculturalism itself," it said.
A Conservative Party spokesman could not immediately confirm the account belonged to the MP, but added: "I would echo David Cameron's words from earlier that this is a great showcase to show what Britain is all about."
The event, in which the Queen had a starring role, featured a diverse cast including James Bond star Daniel Craig and JK Rowling, merging music, dance and special effects into a spectacular opening.
The world-wide audience was treated to a greatest hits medley of British pop over the decades with bursts of the Beatles, the Jam, Sex Pistols and Dizzee Rascal.
There were also excerpts from the Kinks, Frankie Goes To Hollywood and Mud's Tiger Feet before Emeli Sande sang the cup final classic Abide With Me.