Elizabeth Filkin, the new Parliamentary Commissioner for Standards, says she will resign from the building society which loaned money to Mr Mandelson before taking up her post in February.

She says she is keen to ensure her absolute impartiality.

Mr Mandelson resigned from the government on Wednesday after it was revealed that he had taken a £373,000 loan from former Paymaster General Geoffrey Robinson to buy a home in London's fashionable Notting Hill.

Mr Robinson was also forced to resign. A spokesman for Mr Mandelson said his application to the Britannia for the additional £150,000 he needed to buy the house may not have included details of the Robinson loan.

Mr Mandelson cannot remember the details of his mortgage application

Ms Filkin said she has no responsibility for mortgage business and added no-one has yet made a formal complaint to her about Mr Mandelson so no investigation was scheduled, as yet.

"Let's be clear about this. I have not had a complaint to date, therefore I have no investigation on my plate.

"What I do have is a letter from a member of Parliament asking my advice and as soon as I take up my position I will write to him with the advice he seeks."