The Royal Bank of Scotland (RBS) consortium trying to gatecrash the £80 billion merger talks between Barclays and ABN Amro could have its approach scuppered on competition grounds.

European and Dutch monopolies regulators are expected to investigate the impact of the deal, which would, if successful, give Fortis, a member of the RBS consortium, a stranglehold in parts of the Dutch banking market.

Under RBS’s three-way break-up plan, Fortis would take ABN’s domestic banking operations, while Santander, the Spanish owner of Abbey in the UK, would get the Brazilian bank. RBS would take control of LaSalle, ABN’s bank in the United States, along with its investment banking operations.

However, market share figures indicate that Fortis, combined with the domestic operations of ABN, would have a dominant position in small business banking, with 40 per cent of the Dutch market.

There would also be concerns about the large corporate banking market, where its share would reach 43 per cent, and about the credit cards and mutual funds markets (31 per cent in both cases).

Other Dutch financial groups would be likely to protest, compelling Fortis at least to divest some assets and possibly derailing the consortium altogether.

Senior managers from Barclays and ABN were locked in discussions yesterday, trying to thrash out an agreed merger deal and a mutually acceptable price.

ABN shares shot up to €36 (£24.53) on Friday after RBS’s interest emerged. Analysts say that Barclays will struggle to justify paying more than €35 a share, although it is understood to have identified bigger-than-expected synergies from a combination, which might enable it to offer more.

Even if a deal with Barclays can be agreed in the next few days, ABN will have to give consideration to the RBS approach. The exclusivity arrangement with Barclays expires on Wednesday.

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