Kahn will now lead the acquired business.

Existing finance director Mark Dann and head of operations Ian Ryder will support the new chief executive, who says he plans to use Cardsave to make several acquisitions in the financial services market.

The company was sold by a consortium of shareholders including RJD Partners, Morley Fund Management and Lloyds Development Capital.

The deal was financed from Exponent’s sole investment fund of £400 million, which closed in 2004, and backed by debt and mezzanine finance provided by Lloyds TSB. The amount paid for Cardsave is undisclosed.

Exponent has completed six investments so far, which include the acquisition of TSL Education for £235 million, a management buy-out at Discovery Group for £82 million and the takeover of Trainline from Virgin for £163 million.

Cardsave has been providing credit card terminals to independent retailers across the UK since 1995. Today the company services more than £2 billion worth of transactions each year.