AMSTERDAM (Bloomberg) — Fortis, the financial-services company that set out in June to raise 8.3 billion euros ($12.2 billion) to bolster capital, fell the most since it was formed 18 years ago on concern it needs help with funding.

"The rumours about the Dutch regulator calling upon Rabobank Groep to support our liquidity are not true," Filip Dierckx, head of Fortis' banking unit, said in an interview today. "This speculation pushing down the shares is unacceptable."

Fortis dropped as much as 21 percent, the biggest drop since the company was formed in a 1990 merger.

Chief executive officer Herman Verwilst told De Telegraaf on September 20 the company may sell more assets than anticipated as it becomes harder to raise capital in other ways. It needs to replenish capital after paying 24.2 billion euros for part of ABN Amro Holding NV and writing down 682 million euros on structured investments this year.

Fortis has about 3 billion euros of bonds maturing this year and needs to refinance an additional 7 billion euros next year, Ivan Lathouders, an analyst at Banque Degroof SA in Brussels, wrote in a report this week. The company was formed in the merger of Dutch insurance company NV Amev, Belgian insurer AG Group and the Dutch bank VSB.

Fortis traded down 1.16 euros at 5.81 euros at 3:42 p.m. in Brussels. The stock is down 67 percent this year, valuing the bank at 14.1 billion euros and making it the third-worst performer in the Bloomberg Europe Banks and Financial Service Index, down 36 percent.

The decline is "linked to rumours that every Belgian citizen is frightened by Fortis," said Scander Bentchikou, a Paris-based analyst at Oddo Securities who has a "buy" on the stock. "Lots of people say they should diversify and fear a drop in the deposit base."