Nine out of 10 law firms offering civil legal aid work will drop the service within the next four years, a poll revealed yesterday.

Most said they could no longer afford to do the work after reforms they claim have already turned huge swathes of Scotland into "advice deserts".

The survey, by the Law Society of Scotland, is the latest evidence of growing discontent among lawyers about the way fees are paid for civil legal aid.

Oliver Adair, a Larkhall solicitor who chairs the society's Legal Aid Committee, said the poll backed anecdotal evidence from across the country. Lawyers, unhappy with the system of block fees for civil legal aid work, are simply declining to take new cases, especially in complex family law.

Mr Adair said: "What we are talking about is a potential problem with access to justice for the most disadvantaged people."

The Scottish Government and Scottish Legal Air Board (Slab) yesterday acknowledged lawyers' concerns and said they were reviewing fees, something welcomed by Mr Adair. However, he added: "The survey results would suggest they have not done enough."

The Law Society survey, of more than 100 firms, found that 92% of those offering civil work for legal aid intended to stop doing so within the next four years. Fully 38% said they would drop the business within a year.

Only 3% of firms polled said reforms of 2003 - when the system of block fees was introduced - had increased their income from civil legal aid. Some 70% said their earnings from such business had fallen. Many firms said the amount of legal aid work they were doing had increased - mostly because rivals had dropped the business.

Of those planning to drop civil legal aid, four out of five said it was for financial reasons.

One firm said: "When it costs £60 or so an hour to pay qualified legal staff to undertake legal aid work, one would have to regard it as pro bono to undertake it at the silly rates offered by Slab."

Another said: "If the funding is not forthcoming, the scheme will simply wither away. That cannot be allowed to happen in a caring legal system."

Other firms said they would only do legal aid work for the most vulnerable, children and adults with incapacity. Money was not the only gripe. Some companies also complained that they were tied up in red tape.

The way lawyers were paid for civil legal aid changed in 2003. Until then they always received a "time and line payment". They still do for some work, from £53.60 to £68 an hour. Most of their fees, however, come in blocks of £19 with no hourly rate.

The Law Society sent the questionnaire to all firms registered to carry out civil legal aid, although not all responded.

A spokesman for the Scottish Government said a review of fees was being carried out, and is due to be completed next month. "We're aware civil legal aid fee levels are a major concern for solicitors. That is why Slab is reviewing the fees paid to solicitors undertaking civil legal aid work to see if the block fee arrangements are providing an appropriate level of remuneration.

"In the meantime, regulations have been laid in parliament this week which will improve payments for undefended (non-divorce) civil actions in the Sheriff Court."

The spokesman also said Slab officials had been in talks with the Family Law Association to look at how lawyers should be paid for the kind of complex cases that are not suited for a block payment. Improvements could be made by the end of the year, he said.

The government has already made some moves to fill gaps left by private law firms pulling out of civil legal aid. Slab, for example, appointed a salaried lawyer based in Inverness, not least to help women who are the victims of domestic violence.

The Law Society poll follows a separate survey carried out by Mori more than a year ago. Mori spoke to around half of all firms then taking part in the civil legal aid scheme.

A spokesman for Slab said: "In our survey 62% said they were certain to or likely to still be doing legal aid work in three years time. Nineteen percent said they were not likely to and just 9% were certain not to."