The takeover of HBOS by Lloyds TSB will come under fresh pressure this week as the Halifax and Bank of Scotland owner faces a possible counter-bid from a mystery foreign suitor while having to write off an estimated £5 billion because of falling asset values.

Jim Spowart, the former chief executive of HBOS’s Intelligent Finance division, confirmed yesterday that he had been approached by an 'international financial institution' with a view to brokering a bid for the bank that would trump the Lloyds TSB offer.

News of the possible counterbid intensified pressure on Alistair Darling to clarify his attitude to a second offer. But Treasury sources claimed that it was not a matter for the Chancellor but for the HBOS board, which has already agreed the £12 billion merger with Lloyds TSB, and its shareholders.

The Times, Daily Telegraph