The competition watchdog has found evidence of dirty practices at two laundry firms, alleging they breached antitrust law.
The Competition and Markets Authority (CMA) has provisionally concluded former joint venture partners Micronclean, formerly known as Fenland Laundries, and Berendsen Cleanroom Services broke competition law through a market-sharing agreement.
According to the watchdog, the two suppliers of cleanroom laundry services - which cater for sterile environments, including pharmaceutical manufacturers and NHS pharmacies - divided up customers between them by geography.
Fenland served customers in an area north of a line "broadly between" London and Anglesey, whilst Berendsen served customers south of that line, the CMA said.
Other customers were allegedly divided up between the parties based on the nature of their business or the product or service they required.
The alleged arrangement, the CMA claims, prevented each company from supplying customers which were located outside their designated areas.
Ann Pope, the CMA's senior director of antitrust enforcement, said: "However they arise, market-sharing agreements are a serious breach of competition law, which usually deny customers the benefits that arise from competition - such as lower prices, greater choice and innovation and improved service.
"We allege that even though these two companies could have supplied all relevant types of customer, including customers outside each party's designated area, they instead agreed not to compete.
"These are provisional findings only and no conclusion can be drawn at this stage that there has been a breach of competition law. We will carefully consider any representations from the parties before deciding whether the law has been broken."