The British Olympic Association said it would look again at the wording of the agreement after a furious outcry from human rights groups and Opposition politicians.

The angry reaction came after it emerged officials have inserted a new clause in the contract Olympians must sign before competing in this summer's games insisting they must not comment on politically-sensitive issues during the Games. Athletes who breach the contract could face being sent home.

It read: "(Athletes) are not to comment on any politically sensitive issues." It also refers athletes, likely to include marathon runner Paula Radcliffe and the Queen's granddaughter, Zara Phillips, to Section 51 of the IOC charter which restricts demonstrations of "political propaganda" on Olympic sites.

Initially, BOA bosses denied trying to gag competitors, insisting they were free to answer questions but should not use the Games as a soapbox for political concerns.

But chief executive Simon Clegg later conceded that the contract would need to be amended to make its intentions clearer. "I accept that 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," he said in a statement.

The row-back came after response to the move, revealed in the Mail on Sunday, was unfailingly critical. The Liberal Democrat leader told BBC1's Politics Show the decision was a "real abdication of our moral responsibility".

Shadow culture secretary Jeremy Hunt urged the BOA to withdraw the "ridiculous contract".

A spokesman for the human rights group Liberty said: "It would be both un-British and un-Olympian to attempt to muzzle the speech and conscience of athletes attending these Games."

Amnesty International campaigns director Tim Hancock said: "People in China can't speak out about human rights without fear of reprisals; people in Britain can. It's up to each individual to decide what they think and what they say about China's human rights record and that goes for athletes too."