A watchdog will set out how competition can be improved in the £11 billion private motor insurance market in a finalised report tomorrow.

The Competition and Markets Authority (CMA) unveiled a string of proposals for a crackdown in June which could wipe around £20 off the cost of a typical driver's premium if they are put into action, according to estimates by industry experts.

The proposals, which have been subject to a consultation, include ending ''price parity'' agreements between comparison websites and insurers. These agreements block insurers from making their products available to consumers more cheaply elsewhere.

The CMA has said consumers should also be given clearer information about their rights following a motor accident and better explanations of the costs and benefits of taking out protection against their no claims bonus.

Another proposal the CMA put forward was to cap the cost of providing a courtesy car following an accident. The CMA found there was often little incentive to keep this cost down due to a divide between who organises the courtesy car and who pays for it.

Often, while it is the insurer of the innocent party in a car accident which arranges for their car to be temporarily replaced and repaired, it is the insurer of the driver deemed to have caused the accident which picks up the tab.

However, a further paper published by the CMA in July cast doubt over its ability to impose a cap on the cost of a courtesy car and the body said in that document that it was considering alternative measures.

There are more than 25 million privately registered cars in the UK. The average cost of comprehensive cover has already plummeted by 19.3% in the year to June amid industry reforms to combat fraudulent car accident claims, according to figures recently published by AA Insurance.

The typical annual cost of cover for someone who shops around for their car insurance has fallen to £504.

The CMA's proposals have received broad backing from insurers - as well as brokers, who are hopeful that the moves will help them to offer some cheaper deals than those on comparison websites.

Simon Douglas, director of AA Insurance, said previously: "The CMA's recommendations could, it's estimated, wipe perhaps a further £20 or so off the average premium."

Graeme Trudgill, executive director at British Insurance Brokers' Association, has said of the potential impact of the proposed changes: ''If a customer walks into a broker's office, we believe they should be able to offer the premium at a cheaper price than on a comparison site which typically charges around £40 to £50 per lead."