Two of Switzerland's top financial concerns, bank Credit Suisse Group and insurer Winterthur Group, said yesterday they would merge to form one of the world's leading providers of hybrid "bancassurance" services.

The two blue chips said the merger was voluntary but they had hurried to avoid the prospect of a Winterthur takeover by Swiss investment banker and shareholder activist Martin Ebner.

The merger, which needs approval from shareholders and regulators, would make CS Group the biggest Swiss bank and the world's third largest asset manager for private and institutional investors, with $465 billion (£323 billion) under management.

Mr Lukas Muehlemann, CS Group chief executive, also told a news conference the new group would be one of the world's 10 biggest financial services companies with a stock market capitalisation of some $37 billion.

"The merger is a powerful, forward-looking response to developments in the financial services market," said Mr Muehlemann, who will also be chief executive of the combined group.

The merger illustrates the blurring distinction between banks and insurance companies as competition heats up to offer customers one source for a wide range of financial services, often dubbed bancassurance.

Executives said the merger grew out of 18 months of co-operation in three joint ventures.