The BBC, ITV, BT and sports production company IMG have been fined £4.2m for illegally sharing information about fees for freelance workers at football and rugby matches.

The sharing of information, which breached competition law, affected workers such as camera operators and sound technicians, according to the Competition and Markets Authority (CMA).

The regulator opened an investigation into possible cartel-like behaviour in 2022, after it was tipped off by Sky, which broadcasts hundreds of Premier League football matches each year.

Sky was found to be the most persistent offender, with 10 instances of anti-competitive behaviour, but it escaped a fine by alerting the CMA itself.

Producers at the broadcasters shared pay details with one another to try to limit pay for the freelancers on whom much of the TV industry depends. The CMA said that “in most cases, the explicit aim was to coordinate how much to pay freelancers” between 2014 and 2021.

One unnamed business told another they have “no intention of getting into a bidding war” but “want to be aligned and benchmark the rates”. Another company said it wanted to “present a united front” with its competitor.

BT, which has since stopped broadcasting sport, will pay £1.7m for six infringements. IMG will also pay £1.7m, the BBC £424,000, and ITV £340,000. All the companies received discounts for settling early.

Juliette Enser, the CMA’s executive director for competition enforcement, said: “Millions watch sports on TV each day, with production teams working behind the scenes to make this possible, and it is only right they are paid fairly.

“Companies should set rates independently of each other so pay is competitive – not doing so could leave workers out of pocket. Employers must ensure those who hire staff know the rules and stick to them to prevent this happening in the future.”

However, the CMA said it had closed a separate investigation into production companies beyond sports. The regulator said it had not reached a decision on whether the companies had engaged in anti-competitive practices.

The companies under investigation were: the BBC; Hartswood Films; Hat Trick Productions; ITV; Red Planet Pictures; Sister Pictures; and Tiger Aspect Productions.

All of the sports production companies were contacted for comment.

A BBC spokesperson said: “The BBC takes its competition law obligations seriously and has cooperated with the CMA throughout its investigation. We highly value the freelancers we work with.”

ITV declined to comment.