Administrators of the London arm of Lehman Brothers said the claims it is handling against the collapsed Wall Street bank could total as much as $100 billion.

PriceWaterhouseCoopers, which is working with over 100 companies, mostly in the UK but also in continental Europe, said on Sunday: We're dealing with a large number of entities and therefore the claims could be as much as $100 billion.

These claims are exceptionally complex and we anticipate a large amount of further work in dealing with (them).

A significant amount of the claims arose as a result of guarantees issued by the parent company to its subsidiaries, the administrator said.

PwC said it had worked with administrators in other affiliates to understand Lehman's accounting system so a standard approach to the reconciliation of inter company balances could be agreed.

If this can be achieved then it should reduce the likelihood of affiliates suing each other in pursuit of amounts that are owed between the different Lehman estates, it added.

Lehman Brothers Holdings filed for Chapter 11 bankruptcy protection in September 2008, the high water mark of the credit crisis.

Employees, counterparties and creditors have until September 22 to submit claims with the U.S. bankruptcy court.

(Reporting by Rosalba O'Brien; Editing by Mike Nesbit)