The Competition and Markets Authority has back-tracked on plans to place a cap on replacement car and repair charges, which it originally thought would help steer down the price of premiums for UK motorists.
The decision drew accusations that the watchdog had 'ducked the challenge' and would be bad news for honest motorists.
This summer, the FCA proposed that a cap be placed on the cost of replacement cars for at-fault drivers, but it subsequently found that such a measure would require a significant change in the law.
In its final report on the issue, published today, the CMA said the cap could not be justified as the problem only caused an increase in the average premium of £3 per year. It is, however, encouraging some action by those with the ability to make the market work better within the existing legal framework.
Alasdair Smith, chair of the private motor insurance investigation group and CMA deputy panel chair, said: 'We have looked very hard at resolving the problem with the cost of post-accident services to drivers who are not at fault in an accident, in particular temporary replacement cars.
'Reluctantly we have had to conclude that we cannot see an effective way of addressing this problem fully short of a fundamental change in the law and, whilst this problem does increase premiums for motorists, the extent of the problem is not as high as was at first envisaged and does not warrant such a radical measure.
'However, we do wish to challenge the benchmarks typically used in awards for non-fault replacement cars, which do not reflect the cost of the services provided and which we think should be lower.'
Alongside this, the CMA published further measures which it expects will increase competition in the market and bring down premiums for drivers. The watchdog confirmed that it would ban exclusive pricing deals between motor insures and price comparison websites.
The CMA said such deals were stopping insurers from making their products available more cheaply on other online platforms.
Also, it said better information on the costs and benefits of no-claims bonus protection should be provided to consumers.
The watchdog is recommending that the Financial Conduct Authority looks at how insurers inform consumers about other products sold as add-ons to car insurance policies.
Smith noted that the way motor insurance-related add-on products were sold made it hard for customers to obtain best value.
He said: 'There are over 25 million privately registered cars in the UK and we think these changes will benefit motorists who are currently paying higher premiums as a result of the problems we've found.'
Commenting on the report, the Association of British Insurers said the 'U-turn' on the proposed cap was likely to lead to higher charges for customers.
James Dalton, ABI's head of motor insurance, said: 'The fact that [the CMA] fails to do anything to address the excessive costs of replacement vehicles - a problem that the CMA itself identified - will be a bitter pill to swallow for honest motorists.
'The reality is that the CMA has ducked this challenge and when regulators fail, politicians need to step in to act.'