ABN Amro yielded last night to shareholder pressure to open its books to the Royal Bank of Scotland bidding consortium by waiving a key blocking condition.

Less than 24 hours after receiving a drubbing from angry shareholders at its annual meeting, the ABN board said it was dropping the condition that the RBS group must promise not to mount a hostile bid for 12 months before being granted access to ABN’s books.

In a statement, ABN made clear that while it was prepared to explore the RBS approach in a constructive way, it preferred the merger offer from Barclays and accused the RBS group of being uncooperative.

“Despite repeated requests, the consortium has to date not provided us with any clarification on its indicative proposal, . . . implications for staff and clients, regulatory issues, execution risk and other possible conditions,” ABN said.

The waiving of the “standstill agreement” means that RBS and its merger partners, Banco Santander and Fortis, can see the ABN books and still make a hostile offer. It is understood that ABN sought agreement from its preferred merger partner, Barclays, before agreeing to remove the condition.

Accountants and lawyers in the RBS grouping were immediately allowed to examine ABN internal figures last night.

Earlier yesterday, the consortium, which is advised by Merrill Lynch, said that it had told ABN of its plans to make an offer for the whole group – a precondition for making a hostile offer. Under Dutch rules, bidders have to give seven days’ notice before launching a hostile bid and cannot name a price in the meantime.

However, the RBS group said that it invited ABN shareholders to refer to an earlier announcement, in which it set an indicative price of €39 a share, or €72 billion (£49 billion). The ABN move pitches RBS head-to-head against Barclays’ offer of $67 billion (£33.5 billion).

All eyes today will be on the Amsterdam Court of Appeal, where the Dutch shareholder VEB is attempting to freeze ABN’s planned sale of its American bank LaSalle. That $21 billion side deal is still seen as a major impediment to a successful bid by the RBS group, because LaSalle is regarded as the main prize for RBS.

VEB is asking the court to declare the LaSalle sale illegal because ABN shareholders were not consulted. Bank of America, which signed the deal to buy LaSalle, is likely to fight to enforce what it sees as a legally binding contract.

RBS shares fell 30p to £19.40 yesterday.

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