The world's last bastion of free speech? Enter the Cheeky Girls ...

It hosted Nixon's first speech post-Watergate, so do the Oxford Debating Union's latest guests reveal a dumbing down?

The Oxford Debating Union, once described by Harold Macmillan as "the last bastion of free speech in the Western world", is struggling to restore its reputation after a week when its president barely clung on to his job, and a quarter of the audience walked out rather than staying to listen to the union's "celebrity" speakers.

The society has played host over the years to some of the greatest minds and most celebrated names in the world. Richard Nixon made his first public speech there after being removed from the White House. When the Oxford Union voted in 1975 in favour of joining the EU, the result was reckoned to have had a major impact on the referendum. When the union passed the motion in 1933 that "this House will under no circumstances fight for King and Country" it helped convince Neville Chamberlain appeasement was his only option.

This week's clash of minds pitted the Cheeky Girls, whose most famous phrase is "touch my bum", against Rebecca Loos, best known for her alleged liaison with David Beckham. But before they were allowed to make their contributions to a debate on whether "with celebrity comes great responsibility", they had to sit through a rancorous argument between the students.

The Romanian-born Cheeky Girls, who spoke alternately, argued that celebrities should be better behaved.

"We firmly believe that celebrities have a moral responsibility to set a good example," Gabriela Irimia declared. She is the Cheeky Girl who recently had a relationship with the Liberal Democrat MP Lembit Opik. She added: "You don't find pictures of us in the tabloids falling out of the clubs at four o'clock in the morning. If we behaved like that, we would definitely get more press."

Her twin sister Monica created a sensation last week when pictures of her posing naked were all over the press.

On the other side, Rebecca Loos put up a decent defence of the issue of badly behaved celebrities. "Most of the human condition is to be engaged in mundane tasks," she said. "Those who may be regarded as celebrities, or have celebrity thrust upon them, have a duty to behave as irresponsibly as possible.

"Watching a celebrity in meltdown – it's an uncomfortable thing to watch, nevertheless we're drawn to it."

However, for the student audience, the main matter of interest was not the behaviour of the famous, but the future of the 21-year-old Union president, Joshua Roche, who had led them to expect a list of glittering guests this term, including Viktor Yushchenko, Valéry Giscard d'Estaing and Jude Law. None turned up, and most apparently were never asked. Mr Roche survived a move to sack him by 151 votes to 56. After the vote, about 60 students walked out rather than hear their guests.