The regulator says the merger “substantially lessens competition in the supply of property search services in England and Wales”.

TM Group agreed to be bought by Dye & Durham for £91.8m last July. Both businesses offer property search services to conveyancers, solicitors, estate agents, and mortgage brokers on behalf of people and businesses buying and selling properties in the UK under a variety of different brands.

The watchdog says: “The firms were close rivals before the merger and the evidence shows that the combined business would be the largest provider in the market.

“The CMA also found that the merger would only leave two other large national suppliers in the market and that competition from smaller suppliers would not offset the competition lost by the merger.

“The CMA has therefore concluded that the merger would reduce competition and could lead to less innovation, higher prices and lower quality services in the market. This could mean a worse deal for people and businesses buying or selling residential and commercial properties in England and Wales.”

The watchdog concludes that Dye & Durham must sell TM Group to a suitable buyer that it approves of.

Chair of the independent CMA group conducting this inquiry Richard Feasey says: “The merger of two of the biggest players in this market would be bad news for anyone buying or selling property in England and Wales.

“Competition drives innovation and keeps prices down. Without it, we can pay more for worse products and services.”