The unusual move follows an internal investigation into whether Mandelson misled the society on his application form for a pounds 150,000 mortgage to buy his fashionable Notting Hill home.
The Britannia executive is to discuss whether to refer his file to the police at a closed board meeting early next month. This will be the second time that the Britannia board has discussed the Mandelson affair, the Independent on Sunday has learned.
The building society has sought advice from City law firms about whether Mr Mandelson, who took out a secret pounds 373,000 loan from millionaire Labour MP Geoffrey Robinson to help buy the house, misled it.
Mr Mandelson's customer file, which contains copies of his original mortgage application, the deeds of his house and letters confirming his financial status, has been removed from the vaults at the society's headquarters in Leek, Staffordshire. Sources close to Britannia say that the documents have been placed in a safe.
During the days before Christmas, when it emerged that the former Trade Secretary had secretly taken a substantial second loan to buy his house, directors were assured at a board meeting by the Britannia chief executive, John Heaps, that the Mandelson affair was being dealt with "properly and confidentially".
Since that meeting, Britannia has been conducting an investigation into whether Mr Mandelson declared the pounds 373,000 loan from Paymaster General Geoffrey Robinson on his mortgage application form.
The former Trade Secretary resigned from his Cabinet post on 23 December following the revelation of the loan from Mr Robinson, who resigned as Paymaster General the same day. In his resignation letter Mr Mandelson insisted he had done nothing improper.
Mr Mandelson, who said at the time of his resignation that he could not recall whether he had mentioned the Robinson loan on his mortgage application form, has written to the building society giving a full account of the funding of his pounds 475,000 West London home, according to a political aide.
The board will also discuss the public relations implications of the affair and the way the society has handled it.
Although it is expected that the board will agree that the society's interests have not been damaged by any loss of money, the issue of what was disclosed on the mortgage form remains a key issue. Most mortgage lenders demand full disclosure of all financial commitments of an applicant before granting a loan.
The normal maximum advance from a building society is three times an applicant's salary. But Mr Mandelson borrowed more than 10 times his salary from Geoffrey Robinson to buy his house. In 1996, when he obtained the loan, he was earning an MP's salary - just over pounds 34,000.
Mr Mandelson has said he has paid back more than pounds 40,000 of the Robinson loan and was in the process of paying off the outstanding pounds 332,000 with the help of his mother.
The building society has resolutely refused to discuss the details of the application or even to confirm that Mr Mandelson holds an account with it.
A spokeswoman for the society, which has 1.5 million members, confirmed that a board meeting will be held in February but refused to discuss its agenda. She said: "We treat all our customers exactly the same."
Elisabeth Filkin, a director of the Britannia who becomes the new registrar for members' interests at the House of Commons next month, is expected to step aside during the board meeting because of a possible conflict of interest.Reuse content