An ABN Amro shareholder group has come out fighting after an adviser to the Netherlands' supreme court said an earlier ruling to put the sale of US unit LaSalle to a vote should be overturned, appearing to deal a body blow to Royal Bank of Scotland's hopes of acquiring the Dutch bank.

ABN agreed a $21bn (€15.6bn) deal to sell LaSalle to Bank of America in a side deal to the Dutch bank's agreement to be bought by Barclays in April. The LaSalle deal was subsequently challenged by shareholder rights group VEB who claimed ABN was trying to thwart a bid for the Dutch bank from an RBS led consortium.