The National Union of Journalists has claimed that the BBC is falsely inflating the size of its pension fund deficit to justify cutbacks in pensions provision for staff.
The NUJ claims it has seen leaked figures which place the deficit at £1bn, rather than the £2bn which has been claimed by the BBC.
BBC Trustee Jeremy Peat said in response to the NUJ claim: "We are only beginning discussions with our actuaries over the deficit. I have discussed no figures as yet with the BBC but this figure of £1 billion is not one I recognise."
The more than 3,000 journalists at the BBC have voted in favour of industrial action and are set to hold a 24-hour work to rule on 22 October in protest at the pensions changes.
NUJ general secretary Jeremy Dear said: "The BBC sought to sell its pensions robbery by claiming it had to plug a £2bn deficit. If today's figures are true, that has now been exposed as a sham. The BBC's credibility is in tatters and their justification for these punitive changes completely undermined. They must now come clean and re-start negotiations with everything on the table."