The reward is being highlighted as the CMA launches its first-ever advertising campaign to stamp out cartel activity.

It applies to all industries but recent research by the cartel-busting authority highlighted construction as most at risk to anti-competitive behaviour.

This research revealed that 44% of businesses who had been in contact with others in their industry – who weren’t their suppliers – were in contact in relation to a transaction and approaching one in 10 openly reported that they had discussed prices. This rose to 22 % for the construction sector.

Construction also exhibited the strongest signs of anti-competitive behaviour with over two-fifths of businesses feeling they had been disadvantaged through the non-compliant behaviour of competitors.

The CMA’s campaign ‘Cracking down on Cartels’ will encourage people who have witnessed illegal activity to report it, by offering a reward of up to £100,000 as well as promising them anonymity.

Andrea Coscelli, acting chief executive, said: “Cartels are both harmful and illegal, and the consequences of breaking the law are extremely serious. That is why we are launching this campaign – to help people understand what cartel activity looks like and how to report it so we can take action.”

Businesses found to have been involved in illegal cartels can be fined up to 10% of their annual turnover, while individuals can face up to five years in prison and directors can be disqualified from holding director positions for up to 10 years.

These can be reduced or eliminated altogether where a business or individual reports their involvement in a cartel and co-operates fully with the CMA’s investigation.

To report a cartel: email cartelshotline@cma.gsi.gov.uk or ring 0800 085 1664 or 020 3738 6888.