Food delivery giant Just Eat, funeral firm Dignity and motor platform Autotrader are among five firms under investigation by the UK’s competition watchdog as part of its crackdown on fake and misleading online reviews.

The Competition and Markets Authority (CMA) said it had launched probes against the companies – also including customer review and feedback firm Feefo and Pasta Evangelists – to see whether consumer laws have been broken.

Since April last year, companies have been banned from certain tactics around online reviews under law, such as fake posts, paid-for reviews that are not clearly marked as incentivised, as well as for hiding negative feedback.

Sarah Cardell, chief executive of the CMA, said: “Fake reviews strike at the heart of consumer trust – with many of us worrying about misleading content when looking at reviews online.

“With household budgets under pressure, people need to know they’re getting genuine information – not reviews or star ratings that have been manipulated to push them towards the wrong choice.

“We’ve given businesses the time to get things right. Now we’re deploying our new powers to tackle some of the most harmful practices head on.”

The CMA said it was looking into whether Just Eat’s ratings system had inflated some restaurant and grocer star ratings, giving a misleading picture of quality.

For Autotrader and Feefo, the CMA is investigating whether a number of one-star reviews – moderated by Feefo, which handles reviews for the new and used car site – were hidden on the platform and did not count towards the star ratings.

Dignity is under investigation by the CMA into whether it asked staff to write positive reviews about the firm’s crematoria services.

And artisan fresh pasta chain Pasta Evangelists is being probed over allegations it offered customers discounts for leaving five-star reviews on delivery apps without this being disclosed.

If the CMA finds the firms have broken the law, it can order them to change their practices and fine them up to 10% of their annual global sales.

An Autotrader spokesperson said: “We endeavour always to operate as a responsible and compliant business and will co-operate fully with the CMA’s investigation.”

It comes after the CMA recently secured commitments from Google and Amazon to beef up their systems to identify and remove fake reviews.

Amazon last June agreed to put in place “robust processes” to quickly detect and remove fake reviews alongside sanctions for rogue sellers and businesses after an investigation by the CMA to curb the customer hazard.

The tech giant said it would sanction businesses that boost their star ratings via bogus reviews or catalogue abuse, including bans from selling on the website, while users could also be banned for posting fake reviews.

Consumer group Which? welcomed the investigations and said the CMA must “get tough” on firms found to be breaking the law with reviews.

Sue Davies, head of consumer rights policy at Which?, said: “Investigations are a welcome first step, but enforcement will be key – the regulator must be prepared to get tough, use its powers and issue serious fines if these companies aren’t playing by the rules.”

The CMA said it swept more than 100 review publishers as part of the clampdown and sent advisory letters to 54 firms to improve their compliance with the law, with 90% having made changes in response and 75% telling the watchdog they better understood the rules.