The Office of Fair Trading has said it has “reasonable grounds to suspect” that information on pricing was passed between leading supermarkets and suppliers, according to the Financial Times.

Earlier this year the watchdog raided the UK’s big four supermarkets, as well as manufacturing giant Procter & Gamble, and requested information on other companies including Unilever, Coca-Cola, Nestle and Cadbury.

The OFT has now written to the companies to keep them informed about its “ongoing investigation into potential breaches of competition law by a number of retailers and suppliers”.

The cartel investigation reportedly covers dozens of grocery products, although no company has been accused of breaking the law at this stage.

Any company found guilty of breaching competition law could ultimately face fines worth up to 10% of turnover.