Excessive delays are the top gripe consumers have with solicitors, according to research.
Which? surveyed people who were unhappy with their solicitor's service
In a survey of people who had complained of shoddy service, 71% cited delays, according to Which? magazine.
More than half of those surveyed said their solicitor had been negligent, with mistakes coming third.
The Consumers' Association is calling on the government to end self- regulation by the Law Society of solicitors in England and Wales.
A review into regulation of solicitors in England and Wales is currently being undertaken by Sir David Clementi, a former deputy governor of the Bank of England.
Other complaints included solicitors not replying to letters or phone calls.
Over a third of the people who were upset by the service they received said their solicitor treated them with little respect; one woman said her solicitor was "so rude and sarcastic, he left me in tears for days."
But more than 40% of those who said they had received poor service failed to complain.
Which? said the main reason given was that people felt there was little point in complaining.
Others said they would have found it too stressful or upsetting and a few even felt threatened - one said she didn't want to complain for "fear of repercussions".
In response, the Law Society said other surveys had contradicted the report's conclusions, but it did acknowledge there had been problems with its complaints' handling process in the past.
It said: "The Society's performance on complaints handling is improving steadily and we are tackling poor performance by solicitors and providing redress for consumers more speedily and effectively than in the past."