Bookmaker Ladbrokes said Richard Ames, responsible for trading and IT, "has ceased to perform his executive duties with immediate effect."
This comes at a time when the company's online business is struggling to catch up with rivals.
The company declined to comment on the reasons for Mr Ames's departure but said he would remain on the board for now.
The Telegraph reported that Mr Ames had been fired over a botched digital strategy.
His departure comes a little over a year after Gary McIlraith quit as managing director of digital channels, international and strategy.
Ladbrokes, which pulled out of talks to buy online gambling businesses 888 Holdings and Sportingbet last year, had said it would invest £50m over two years to improve the performance of its internet business, which has lagged that of rival William Hill.
The company warned last month that profits from its digital division would fall more than expected in the first half due to a delay in technology upgrades and a poor sportsbook margin.
William Hill, on the other hand, said last week that revenue at its online operation rose 30%.
Shares in the Ladbrokes, which is due to report interim results on Thursday, were down 5% at 155.2 pence at 1328 GMT on the London Stock Exchange.
