The 'Go for Gold' scratchcard will go on sale tomorrow, the first of several dedicated National Lottery games which aim to raise £750m.

A further £750m will also come from via Lottery channels, £340m from Sport England and £410m diverted from other 'good causes' from 2009 depending on need.

The launch coincided with the first political row of the London Olympics as opposition leaders immediately criticised the Government's decision to tax the Olympic Lottery games.

Sebastian Coe, London 2012 chairman, would not be drawn on the dispute but hailed the launch of the scratchcards.

Lord Coe said: "Seven years from today we will be just a few hours away from welcoming the world to the opening ceremony of the London 2012 Olympic Games.

"The new Go for Gold scratch cards will provide key funding to make the Games happen. These will be magical Games."

The main cost will be the construction of the new Olympic Park containing the Olympic stadium and athletes village, which will transform the Lower Lea Valley, a high priority regeneration area.

Work has already got under way for the Olympics aquatic centre, and Coe inspected progress today before going to the Lottery launch.

Lottery operators Camelot will seek approval from the National Lottery Commission and the International Olympic Committee for other lottery games, likely to include a new draw-based game next year and even London 2012-themed television game shows.

Tessa Jowell, the Olympics minister, admitted the cost of staging the Games could go up in the wake of the London bombings.

She said: "Security will be designed in to every one of the Olympic venues and to the Olympic village. Of course it's a major challenge.

"The best way that our allies can show their solidarity with the people of London, particularly those families who lost their loved relatives on July 7, is to come here and support us."

The Government had estimated the security bill would be about £200m, but Jowell, asked if the amount of money needed for security would increase, said: "It may do. Neither you nor I know what the security situation at that time will be. But the very clear assurance that we have given is that the games will be both policed and the security will be operated at a level which is consistent with risk at the time. And if there are additional costs to be met, they will be met."