'There was no external pressure, none whatsoever, for us to make the amendments in the contract. It was an internal decision,' Graham Newsom, the BOA head of communications, told the South China Morning Post. 'We accept we drew up the new clause in part because the Beijing Olympics is attracting a high level of political interest.'

The proviso warned athletes they would be banned from travelling to China if they refused to sign and agree to remain silent on political issues. It also threatened to send home anyone who broke the muzzling order.

The controversy caused an uproar in Britain and yesterday the BOA was forced into a humiliating U-turn, saying it would carry out a review and tone down the contract terms.

Newsom said the clause, written into the wide-ranging 30-page contract, was also to 'reflect and was in reference to' Section 51 of the Olympic charter, the International Olympic Committee's set of rules which bans athletes from political and racial protests and religious propaganda.

'We have new members and wanted to make them aware of the Olympic charter' as well as making changes because the Beijing Games 'are highly politicised', he said.

Newsom played down the mounting anger, led by the Mail on Sunday, which likened the clause to an order given to the England football team to give a Nazi salute at a match in Berlin in 1938.

Opposition Conservative Party sports spokesman Jeremy Hunt demanded the BOA withdraw the 'ridiculous requirement'.

Newsom said: 'We have plenty of time to review and amend the clause as only nine athletes [from the sailing squad] have so far qualified and are eligible to sign it.'

He said he would not comment on 'hypotheticals' but said punishment against a dissident UK athlete would be decided 'at the time' of the offence. 'We have not earmarked any athletes. Most just want to compete,' he added.

As the storm intensified on Sunday, BOA chief executive Simon Clegg said: 'The interpretation of one part of the draft BOA's Team Members Agreement appears to have gone beyond the provision of the Olympic charter.

'This is not our intention, nor is it our desire to restrict athletes' freedom of speech and the final agreement will reflect this.'

Had the BOA stood firm and made all Olympians sign the silencing order, they would had found an ally in Beijing Olympic organiser Bocog, which is worried about sports stars protesting, and have been backing a universal ban on political dissent by athletes attending the Games.

Bocog spokesman Sun Weide made no direct comment on the British fallout, but instead repeated the government line that all athletes were expected to follow the Olympic charter. 'I hope the Olympic spirit will be followed and also the relevant IOC regulations will be followed in every regard,' he said.

IOC spokeswoman Emmanuelle Moreau said the charter applied to all Games and all athletes were expected to adhere to Section 51.

'The IOC does not have any say in what a National Olympic Association puts in its contract as it is closer to its athletes. It's natural it would follow the charter. We do ask all competitors take notice of Section 51. But what an athlete says outside of the Olympics and its venues is up to them as that is freedom of expression. Such differences are common sense,' she said.

The BOA rumpus comes less than a week after Ethiopian Olympian and marathon world record-holder Haile Gebrselassie caused controversy with his condemnation of the mainland's pollution record.