Shares in Mantra Group soared more than 16 per cent on Monday after Paris-listed global hotel giant Accor made a $1.2 billion all-cash offer to buy Australia's second biggest hotel and resort operator.

A merger of the country's two biggest accommodation providers would create a local hotel giant with a national portfolio of more than 300 hotels, a dozen or so brands and in excess of 50,000 rooms – about five times bigger than its nearest competitor, franchisor Choice Hotels.