The company said Mr Potts, 41, was leaving to take up a position in the car industry and that his departure was "entirely amicable." However, he will be eligible for compensation for loss of office under the terms of his 12-month contract, which last year paid him pounds 290,000.
"There is no question of a bust-up," Mr Peter Vardy, the chairman, said. "I have known Graeme for years and I wish he'd stay forever. But he has been here 15 years and feels it is time to move on."
The company has courted further controversy with the announcement that Mr Vardy, who owns 30 per cent of the company, will add the chief executive's position to his responsibilities as chairman.
Mr Vardy denied that the company was flouting corporate governance best practice by allowing him to combine the two top roles. He said the balance of power would be maintained by the promotion of Robert Dickinson, a non- executive director, to non-executive deputy chairman.
In a current trading statement, Reg Vardy said trading had been strong this year and sales in March, when the new T registration was introduced, were particularly buoyant.