Changes made by Camelot to its core Lotto game will be used by the rival Health Lottery to launch a major drive to grow market share and ticket sales.

The National Lottery operator is raising the price of a ticket to £2 from this autumn and promises more money for retailers and charity.

Sales director Duncan Malyon refused to speculate on the effect on sales but Camelot is confident of growing revenues with the biggest change to the game since its 1994 launch.

Retailers have welcomed a pro-rata commission increase which will pay 10p per line, but said that they expected to see a drop in the number of tickets sold in a week.

Health Lottery chief executive Dominic Mansour predicts that overall revenue will increase by 35% on Lotto – the equivalent of a ticket sales drop of 32.5% – and is readying a major marketing and advertising campaign to capitalise