UP to 350 jobs are in jeopardy at William Hill after the bookmaker announced plans to move its telephone business offshore and review some loss-making betting shops.

William Hill said 150 jobs could be lost at its Sheffield and Leeds call centres – which together employ 400 staff – as part of a move to establish a new call centre in Gibraltar.

The Leeds centre will close and the Sheffield site will be handed over to outsourcing firm Vertex.

The firm is also reviewing the future of 50 of its 170 unprofitable shops, which it said could put another 200 jobs at risk by the end of the year.

Chief executive Ralph Topping hit out at “unfair pressure” caused by competition from offshore operators and betting exchanges like Betfair, which work under a more favourable tax regime.

William Hill’s telephone betting business lost £1.8 m last year and is expected to make a small operating loss for the first half of 2010.

The business pays 15% gross profits tax and a 10% horse racing levy on its takings.

It has hit out at major players “laying” huge volumes of wagers on betting exchanges, effectively trading as bookmakers but not paying the same charges.