Lehman Brothers in Europe has asked its US counterpart to give back more than $US8bn (€5.5bn) that it says was trapped when its holding company filed for bankruptcy protection in New York a week ago.
Lehman Brothers International in Europe wants the money back even though key US operations will be transferred to British bank Barclays, which is buying Lehman Brothers Holdings' North American banking business.
Some clients of Lehman's European arm believe they could get back more of their money if the cash is moved back to London and they asked a US bankruptcy judge to make sure the money was not absorbed by Barclays.
The money was moved to the US in a routine transaction that happens over the weekends, according to a complaint filed as part of Lehman's bankruptcy proceedings.
After the funds moved to the US on Friday September 12, they may not have moved back, since Lehman filed for bankruptcy - the biggest in US history - before dawn on the following Monday.
The same day as the bankruptcy filing, Lehman in Europe put itself under administration. PricewaterhouseCoopers is the administrator in charge of winding down Lehman's European operations.
In a court filing on Friday, lawyers for Amber Capital Investment Management wrote that there was a risk the £4.5bn (€5.7bn) would be included as part of the Barclays sale.
"The proposed sale transaction with Barclays has moved at a rapid pace and parties have not had an opportunity to trace the LBIE cash and investigate the assets that are proposed to be transferred as part of the sale," the filing said.
A lawyer for Bay Harbour Management, which has used Lehman as a prime broker, argued in court papers that the money may have been "misappropriated".
The lawyer, David Rosner, said the money transfer "may have been manipulated to prop up LBI for sale", although he said there was no way of knowing whether this was the case.
"The Barclays sale threatens to further dissipate the ability of LBIE's administrator and customers to recover their rightful property and to protect Barclays from claims to this cash," Bay Harbour lawyers said in their filing.
James Peck, the judge in Lehman's bankruptcy case in New York, said on Friday that the court would examine the issue in greater detail, but he put it aside so he could focus first on the sale of Lehman's investment banking and trading units as well as certain real estate assets to Barclays.
Judge Peck approved the sale just after midnight on Saturday, and under the agreement with Barclays, the deal must close by tomorrow.
The Sunday Times reported that Japan's Nomura and Barclays might bid for Lehman's British-based equities and investment banking business. The paper also reported that BNP Paribas was interested.
A spokesman for Lehman's bankruptcy law firm in the US, Weil, Gotshal & Manges, did not immediately return calls for comment.
British prime minister Gordon Brown said the British government was working with the US government to get the cash back.
While mistakes had been made in Britain, he said the primary blame for the crisis had to go to the United States and he urged the adoption of international financial regulations.
"It's fair to say also that we're in a new world, and I think what people haven't appreciated is we've now got global financial systems but we've only got national regulators to cover them," Mr Brown told the BBC.
"I've been pressing for some years, and I wish I could have persuaded other countries to do what I wanted, and that was to create a global system of financial regulation."