The Competition and Markets Authority (CMA) has seen a 30% rise in the number of tip offs about cartels.

Now CMA chiefs are turning the spotlight on construction with rewards of up to £100,000 on offer to whistleblowers.

The authority has been handed an extra £2.8m from the government following a string of successful prosecutions.

The new campaign encourages people to be “Safe, not Sorry” if they think they may have involved themselves in cartel activity and to make sure they are the first to report it to the CMA.

Witnesses – those not involved themselves but who have seen something untoward – are also asked to “Do the Right Thing” by reporting it to the CMA.

Stephen Blake, Senior Director for Cartels at the CMA, said: “We are committed to tackling cartels wherever we find them.

“More people are reporting illegal activity to us and we urge anyone with information to come forward.

“If you’re involved, it’s better to be safe, not sorry and to tell us about it first – before someone else does.

“For those who were not involved but have witnessed illegal activity, we urge them to do the right thing.

“We know that this is a sensitive issue and some people could worry about what might happen to them if they speak to us. All information is treated confidentially and we can discuss any concerns that people may have over keeping their identity secret.”

Over the past two years, the CMA has issued £151m in fines following successful investigations into anti-competitive practices and it is currently investigating 15 cases where competition law may have been broken.

The new campaign will target a range of industries that are at a greater risk of cartels forming.

These sectors include: construction, manufacturing and business support services.