William Hill is set to buy Stanley Leisure’s 624 betting shops for £504m, making it the UK’s biggest bookie owner.

William Hill has also withdrawn proposals to return £450m to shareholders in order to finance the acquisition. The sites, will trade under the Stanley Racing and StanleyBet brands once the deal, which is subject to shareholder approval, is complete.

Stanley’s betting shops are predominantly spread throughout the Midlands, the north of England and Ireland. William Hill said the deal would enable it to expand in both Northern Ireland and the republic of Ireland.

Around 50 of the Stanley Leisure sites have already been earmarked for disposal to try and appease competition regulators.

The deal will take William Hill’s estate to more than 2,200 shops.

William Hill chief executive David Harding said: “This represents an opportunity for us to substantially increase distribution.”

An accompanying trading update from William Hill showed poor results for the 19 weeks to 10 May.

It has been speculated that, following the William Hill deal, Stanley, will become solely a casino operator, may merge with rival London Clubs International following the Malaysian gaming operator Genting having purchased substantial stakes in both businesses.