A group of Canadian banks and pension funds mounting a hostile bid for the TMX Group said on Sunday they have added more partners to the effort to top a rival offer from the London Stock Exchange Group .

The so-called Maple Group said Desjardins Financial Group, GMP Capital Inc , Dundee Capital Markets and Manulife Financial had agreed to join the C$3.6 billion ($3.7 billion) bid for the operator of the Canada's main bourse.

Maple Group, which takes its name from Canada's patriotic maple leaf symbol, says their offer is financially superior to the C$3.5 billion bid from the London Exchange and will keep ownership of the TMX within the country's borders.

Maple Group's original members were Toronto Dominion Bank, Canadian Imperial Bank of Commerce , National Bank of Canada , Bank of Nova Scotia , plus five pension funds including Caisse de depot et placement du Quebec and the Ontario Teachers Pension Plan Board.

($1= 98 Canadian cents)

(Reporting Allan Dowd, Editing Marguerita Choy)