ABN Amro has been threatened with a $220 billion (£110 billion) lawsuit — equivalent to the gross domestic product of Greece — if it reneges on a deal to sell its LaSalle offshoot to Bank of America (BoA).

BoA is understood to have told ABN that it will seek damages of this size, which is twice ABN’s entire market value and ten times the $21 billion LaSalle price tag, if for any nonregulatory reason the deal falls through.

Even by the standards of the highly litigious United States, the claim — including punitive damages — would be among the biggest ever corporate compensation claims. The warning came after the Dutch commercial court said at the weekend that it would rule on the legality of the LaSalle deal on Thursday, just a day before it is scheduled to go unconditional.

VEB, the Dutch shareholder group, is pushing to have the deal nullified on the ground that it is a “poison pill” designed to support ABN’s planned €140 billion (£95 billion) merger with Barclays, preventing the fullest value being generated for ABN shareholders.

The rival bidding consortium of Royal Bank of Scotland, Banco Santander and Fortis is continuing its due diligence of ABN and LaSalle after being given access to the books late on Friday. They have not ruled out making hostile bids for both LaSalle and ABN, each bid conditional on the other, before the Thursday ruling.

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