BDO Stoy Hayward has taken on a ‘poisoned chalice' by agreeing to act as independent valuer of the stricken mortgage lender Northern Rock, shareholders of the bank have said.

BDO was appointed this week to put a price on what Northern Rock would have been worth without government help, to assess compensation for shareholders.

Roger Lawson, chairman of the Northern Rock Shareholders Action Group, said he did not expect much from the valuation process.

‘The valuation process is going to be a nonsense. I don’t know what the valuer’s going to do. Under the government’s terms of reference it basically means that you can tell that the answer is going to be zero within five minutes. It’s nice of [BDO] to take on this poisoned chalice,’ he said.

Though some have estimated the value at 400p a share, others suggest the bank was worthless, meaning BDO could have a tough job arbitrating the issue.

BDO is being paid a fixed fee of £4.5m for the job. It is unclear who BDO’s rivals for the contract were, but Ernst & Young, KPMG and PricewaterhouseCoopers are all thought to have been conflicted.

Former shareholders of Northern Rock include SRM Global, listed hedge fund RAB Capital and Legal & General.

The government’s terms of reference say the company should not be treated as a going concern, which scuppers any chance of a meaningful value being attached to the bank, Lawson said. ‘Who would pay anything for a business that’s not a going concern?’

A Treasury spokesman said:‘It is for the valuer to determine compensation. That is why we have appointed somebody at arms length.’ BDO said it would conduct a transparent valuation.