Moneysupermarket.com became the biggest faller on the FTSE 250 in early trading after the sale of a 6.4 per cent stake in the business was cancelled.
Shares in the business fell 5.5 per cent to 270p - although they have climbed by more than a fifth this year.
The insurance comparison site's founder, Simon Nixon, announced plans to sell 35m shares last night, but this morning a statement by Citigroup, which is acting on behalf of Nixon to sell the shares, said he had "decided not to proceed".
Nixon, who led the company's IPO in 2007, stepped down as its chief executive in 2008. However, he is still thought to own 17 per cent of the company.