The BBC has denied that it told two different stories to the government and employees about why it is sending back-office jobs to India.
Xansa pledged to save the BBC £200m over the contract, partly by sending some jobs to India.
The union claims it was told by the BBC at a meeting on 28 November that the Xansa deal was not the cheapest, and that all the bids had an offshore element.
Bectu then claims that the BBC told the Committee Of Public Accounts (CPA) on 29 November that the Xansa contract was the cheapest. It also claims the BBC told Medas staff in December that a bid from EDS contained no offshoring.
Bectu supervisory official Luke Crawley said: “Bectu is calling on the BBC to own up and tell the truth – either it has lied to Parliament or it has lied to the staff and unions about the contract.”
A spokeswoman for the BBC said: “The BBC refutes the allegation that we misled Medas staff or Parliament over the outsourcing of financial services to Xansa.
“While we appreciate the concern felt by Medas staff as a result of the contract being awarded to Xansa, our first priority is to ensure value for money to licence fee payers.
“Consistent with the BBC’s evidence given to the CPA, the annual service charge of the Xansa contract to the BBC is the most competitive of the four shortlisted bids and provides the best value for money to the BBC. All of the bids evaluated by the BBC contained an element of offshoring.”
It is understood that there is a one-off cost to the BBC of transferring to Xansa, which means it cannot be considered the cheapest in true terms.
“Xansa gave the strongest and best balanced offering and therefore the most economically advantageous solution for the BBC,” said the spokeswoman.