Bettel infuriated many Conservatives after going ahead with a press conference alongside an empty podium where the British leader was supposed to be addressing the media.

Johnson had walked out complaining a noisy anti-Brexit demonstration made it impossible to go ahead.

To cheers from the crowd, Bettel then mounted an emotional onslaught, complaining the future of citizens across the EU was being held hostage for "party political gains".

British officials were said to have asked for the press conference to have been moved inside, only to be told there was insufficient space for all the journalists present.

Pro-Brexit Tory MP Daniel Kawczynski said the scenes underlined the need for Britain to get out of the "artificial arrogant EU structure" as quickly as possible.

"Luxembourg PM representing a nation smaller than Birmingham admonishing and being disrespectful to a British PM for trying to fulfil will of British people. he tweeted.

Even some pro-EU MPs supported Mr Johnson's decision to walk out.

Sir Nicholas Soames, accused Mr Bettel of "unhelpful grandstanding".

"Very poor behaviour by Luxembourg. Boris Johnson quite right not to be made a fool of," he tweeted.

The row erupted as the UK's highest court prepared to consider whether Mr Johnson's five-week suspension of Parliament was lawful.

The Supreme Court in London will hear appeals from two separate challenges brought in England and Scotland to the prorogation of Parliament over three days, starting on Tuesday.

Johnson, who also met European Commission president Jean-Claude Juncker on Monday, insisted a deal was still possible before the UK is due to leave the EU on October 31.

In contrast, however, the commission said it was the UK's responsibility to bring forward "legally operational solutions" to the issue of the Northern Ireland backstop which remains the main obstacle to an agreement.

Australian Associated Press