Winterthur has refused to comment on reports that it plans to sell its UK general insurance arm, Churchill Insurance.
Winterthur spokesman Christian Pfister said: "These are market rumours, upon which we don't comment."
A spokesman for Credit Suisse Group also declined to comment.
Yesterday, the Sunday Times reported Churchill Insurance has been put on the market with a £1.5bn price tag.
The sell-off rumours have been fuelled by speculation that Credit Suisse believes Churchill is one of its most saleable assets.
