Sports shop tycoon Dave Whelan has pledged to hand over the cash within 14 days if a general election is called.

Mr Whelan, the chairman of Wigan Athletic football club, said he had been particularly affected by the case of 11-year-old Rhys Jones, who was shot dead in Liverpool.

"I am supporting David Cameron because having met and talked with him, I am convinced he has the right approach to dealing with law and order in Britain.

"This Government, I believe, has failed on that front and the Conservative Party now stands as the only party prepared to take on these issues.

"The murder of Rhys Jones upset me and my family, just as it did so many people in this country.

"David's promise to deal with knife and gun crime, early release of prisoners and more prison places is music to my ears. He has my full support."

The pledge of money from Mr Whelan - who is not believed to have donated to a political party before - will be a welcome fillip to Mr Cameron, who is expected to have a rough ride when the party meets for its conference in Blackpool next week.

Prime Minister Gordon Brown has been riding high in the polls, with the latest giving him an 11 point lead over the Tories.

There are also increasing signs of disaffection among grass roots and hints of possible friction between the party's senior figures