Boxclever is at the centre of the investigation

In an interview with a Sunday newspaper, Robin Saunders urged her bosses at state-owned WestLB to back her as head of its principal finance unit - or let her buy the business.

The American-born banker also hits back at claims �354m of bad debt at Boxclever, the television rental business owned by Nomura investment bank and Granada, is her fault.

WestLB said on Friday it was launching an investigation into its UK unit after being forced to revise dramatically upwards its loss for last year.

Formula One

The bank, owned by the state of North- Rhine Westphalia, reported a pre-tax loss of 1.67bn euros ($1.94bn; �1.19bn) after in February saying it expected a loss of 1bn euros.

I could do it with a few phone calls but I can't force them (WestLB) to sell it to me Robin Saunders

The difference was because the London-based structured finance unit, headed by Ms Saunders, needed hundreds of millions more euros than previously thought for providing against risks, the bank said.

WestLB's chief executive Juergen Sengera sparked speculation about Ms Saunders' future by apparently dodging an opportunity to publicly back her.

When asked about his support for Ms Saunders, Mr Sengera told a press conference: "There I think we should be fair to all and we should also wait for the result of the investigation there and then we will make a statement."

Ms Saunders made her reputation with the refinancing of Formula One, which turned its owner Bernie Ecclestone into a billionaire.

High salary

She also masterminded a �426m loan for the rebuilding of Wembley stadium and has backed entrepreneur and close friend Philip Green's bids for Arcadia, BHS and Safeway.

But she has also received substantial publicity over unsuccessful - critics say unrealistic - approaches to take over Railtrack and buy BT's fixed-line telephone network.

Some critics have said she has been prepared routinely to take on levels of risk that other banks have not and loaded bought or refinanced firms with too much debt.

They also say the team has yet to convince with its "exit strategy" for investments.

Her high salary - believed to be more than �1m a year - is also said to have caused friction with WestLB's bank managers in Germany, who earn about �70,000 a year.

Reputation

WestLB refused to comment on press reports its German supervisory board was looking for ways to "discredit" its UK operations.

One banker quoted by The Sunday Telegraph said: "It is clear that the supervisory board wants to close down everything outside Germany and her in particular."

Ms Saunders is said to be determined to save her reputation.

In an interview with The Sunday Telegraph, she claimed she could easily find backers for a buyout of WestLB's principal finance unit.

"I could do it with a few phone calls but I can't force them (WestLB) to sell it to me.

"They have to decide. I want to take the positions I have built up with me," she told the newspaper.

When she made a similar offer a year ago WestLB blocked it.

A spokesman told BBC News Online: "It is not necessarily a new idea."

'Mounting concerns'

Meanwhile, the bank's investigation will centre on a �748m bond issue Ms Saunders arranged to refinance Boxclever, formerly known as Radio Rentals.

The bonds are secured against income from Boxclever's TV rental agreements, thought to be about �140m.

But analysts believe the business could struggle to meet its payments in future years as renting TVs falls further out of favour.

On Thursday, credit rating agency Moody's placed WestLB under review for a possible downgrade, citing "mounting concerns over WestLB's ambitious international strategy, especially in the area of project and corporate finance and equity investments".