The move by Bryan Marsal, who heads the firm managing Lehman's US liquidation, underlines tension between the company's creditors and Barclays, which acquired the North American operations of the investment bank for $1.5bn after it filed for bankruptcy in September.
The decision by Alvarez & Marsal, which is charged with recovering funds for creditors, to query Barclays' use of the money could also fuel controversy over the large bonuses paid to Lehman executives who stayed with the UK bank.
In its yearly results last week, Barclays booked a gain of £2.3bn on the difference between the fair value of the assets and liabilities acquired from Lehman and the price paid for them. The gain accounted for about a third of Barclays' pre-tax profits and helped Barclays Capital, its investment banking arm, to record a profit of £1.3bn.