The move represents a potentially fatal blow to the deal, which must be approved at a shareholders' meeting on Wednesday in Brussels. Ping An holds about 5 per cent of Fortis and had refrained from criticising the series of deals that resulted from the group's rescue in October.
It comes after the renegotiation 10 days ago of the sale to make it more attractive to shareholders who in December voted against a proposed new chairman and took Fortis to court to force a vote on the BNP sale.
At that time, Ping An had seemed supportive of Fortis management, but the group, which has seen its Fortis investment lose more than 90 per cent of its value, appears to have been angered at having been frozen out of the deal renegotiation.