The Halifax Labour MP said: "If it turns out Lloyds is the only serious bidder then we know what we are dealing with and can start to have serious talks about how to protect HBOS workers."

Her remarks followed a statement by Gordon Brown in which he dismissed calls for the Lloyds takeover to be scrapped. Despite reports that the Bank of China was in early talks over backing a rival offer, the Prime Minister said there was only one "realistic" option.

The premier said: "There has been no announcement by any financial institution that it is prepared – apart from Lloyds TSB – to take on the problems as well as the opportunities of HBOS.

"I think people have got to be realistic about that.

"It is not going to change much if one person says he wants to take over a bank if they have got no money behind them." Mrs Riordan said her office had been in touch with Sir George Mathewson and Sir Peter Burt, former chief executives of Royal Bank of Scotland and HBOS.

They have voiced opposition to the TSB deal, claiming it would be bad for shareholders and would reduce competition.

Mrs Riordan said: "The Prime Minister is right in that Lloyds TSB is the only serious and funded bidder.

"Everything else I have read and heard at the moment has been speculation."

Lloyds TSB says it will be able to deliver annual cost savings of more than £1.5 billion by the end of 2011 through its deal.
But there are fears it could lead to widespread job losses at the would-be combined banking giant.