Big fraud cases face the threat of delays in the courts as a row escalates between barristers and the government over the launch of competitive tendering for legal aid work.

Many barristers have rejected the proposed new deal, which has triggered a series of bad-tempered exchanges between the Legal Services Commission and the Bar Council.

Tim Dutton, Bar Council chairman, said the dispute could potentially hold up future court cases, although he added that the commission could prevent this by changing the competitive tendering scheme.

He said: ?The scheme was supposed to test the market. If the market has responded in insufficient numbers, then that?s a sign that the test was set wrongly.?

The commission ? which runs legal aid in England and Wales ? admitted that a ?substantial number? of barristers had decided not to sign new contracts they had been offered on the basis of preliminary bids.

The row is the latest in a series of disputes between the government and the legal profession over reforms designed to curb growth of the ?2bn ($3.9bn) legal aid bill.

Last year about 400 defendants in 100 very high cost criminal cases received ?105m of legal aid. The Bar Council has said the proposed fees under competitive tendering would cut barristers? rates by between 2.5 per cent and 14 per cent, with junior lawyers? rates falling to as low as ?43 an hour.

Richard Collins, the commission?s executive director for policy, said he took the dispute ?very seriously?, although he stressed it would be months before it started to affect court cases.

He said: ?What we need to do is take stock on the number of people who have signed up and decide what the best way forward is.