From July 20, Sets will open 30 minutes later at 0900 (BST). The pre-market opening period will also be shortened to 10 minutes.

Since its introduction Sets has proved an embarassment to the LSE.

It has been severely criticised by many City traders who have chosen to bypass the system.

Sets will open at 0900 from July 20

The LSE hopes the earlier opening will help to tackle wide fluctuations in share prices caused by a low volume of trading on the new system, especially at the beginning and end of the day.

It said in a statement that the Sets system was viewed as "sound and technically robust" but "there was a general desire to see more liquidity in the system."

Richard Hunter of Natwest Stockbrokers weighs up the criticism of the system

In a move designed to help private investors, the LSE expects the reforms to lead to more consistent pricing of shares at the start of the day, boosting confidence in the market.

At present there is insufficient trading between 0830 and 0900 to give an accurate reflection of the top 100 stocks.

The LSE is also seeking an alignment of its closing hours with the London International Financial Futures Exchange (Liffe).

Boost to confidence

Robert Giles of Credit Lyonnais "The early opening hours and alignment of closing hours are excellent and very welcome.

"It may not seem that dramatic, but I think this could help to swing sentiment towards Sets.

"If there's more confidence in the system, people use it more and it becomes more liquid and gains more credibility."

The Stock Exchange completed its electronic revolution in trading in October 1997 when it replaced the Seaq system with Sets for the FTSE 100.

However most share trades are still completed through the old trading system introduced more than 10 years ago which use market makers, or intermediaries to deal in stocks.