Shareholders in Fortis, the Belgian bank, will decide today whether to approve a €13 billion (£8.7 billion) rights issue in a landmark vote that is vital to the success of the world’s biggest banking takeover.

Fortis and its consortium partners, Royal Bank of Scotland (RBS) and Santander, the Spanish banking group, are locked in battle with Barclays to buy ABN Amro, the Dutch bank.

If Fortis’s shareholders do not approve the capital raising, to be put to a vote at two special general meetings in Brussels and Utrecht today, the consortium will be forced to decide whether to continue its €71.1 billion pursuit of ABN.

The Fortis vote comes with Barclays due today to outline its bid for ABN. Speculation at the weekend suggested that Barclays would also announce its intention to divest some ABN assets to a partner.

Sir Fred Goodwin, chief executive of RBS, said on Friday that he had not yet formulated a “Plan B” in case Fortis’s management failed to sway its shareholders. “In the unlikely event that we need a contingency plan, we’ll work something out,” he said.

Fortis needs 75 per cent of its investors to approve a rights issue, one of the largest conducted by a European bank, in order to secure its €24 billion share of the consortium’s bid.

Although Fortis’s long-term shareholders have traditionally supported the bank’s management in its 15-year acquisition programme, two or three hedge funds are thought to have been pressing other hedge funds invested in the bank to vote against the rights issue.

Fortis shares have fallen 15 per cent since it became embroiled in the takeover battle for ABN. There has been speculation that Fortis’s shares will fall farther if the capital-raising succeeds, whereas a “no” vote could bolster the bank’s share price.

Rijkman Groenink, head of ABN, had been quoted as saying that Fortis shareholders should vote against the rights issue, but ABN and the RBS-led consortium issued a joint statement yesterday denying this.

Howard Wheeldon, a senior strategist with BGC Partners, the bond broker, said that the consortium may draft in another partner if Fortis has to drop out of the takeover team.

“Each could actually attempt to go it alone with a full bid or merger of sorts, although we think at this stage it is very unlikely,” Mr Wheeldon said.

Barclays is to unveil the formal details of its competing €67.5 billion offer for ABN today. Documents will be sent out to almost 900,000 shareholders, who will be asked to vote on the deal on September 14.

RBS’s shareholders will meet on Friday in Edinburgh to vote on the proposed issuing of five billion new shares in the bank, in order to finance RBS’s €27.2 billion share of its consortium’s offer for ABN.

Investors in Santander have already approved the Spanish bank’s €9 billion refinancing arrangements, including the issue of four billion new shares, needed to fund its €19.9 billion share of the offer.

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