Prosecutors are becoming increasingly concerned about preparation time, staffing levels and workload for cases, a public service union has found.

A survey by the FDA union of members in the legal sector found 81% had concerns, and the union said it should act as a "wake-up call" to ministers.

Almost a quarter of prosecutors, 23%, said insufficient time to prepare cases was a serious cause of stress, and some of those surveyed said it could lead to mistakes in high profile cases.

The union represents around 19,000 civil servants, prosecutors and solicitors. It surveyed 986 staff in the legal sector.

Of those who took part, 46% said they had unrealistic time pressures in work, 33% believe they have unachievable deadlines, and 39% have to neglect some duties because they have too much work to do.

One prosecutor told the FDA: "After many years I am losing faith in the service and our ability to prosecute in the public interest."

FDA Scottish secretary Jim Caldwell said: "This survey shows clearly that there are serious problems within Crown Office Procurator Fiscal Service that need to be addressed urgently.

"These highly-trained legal professionals certainly do not lack skill or motivation, but little time for preparation is seriously damaging their ability to prosecute in the public interest.

"It cannot be acceptable that prosecutors are given less than 24 hours to prepare to take a case to court where the outcome is a possible five-year prison sentence. These cases include crimes of violence and serious sexual offences.

"The administration of justice is vital to public confidence in our legal system. Our members care about this and also care deeply about the victims of crime they see in our courts every day. That is why so many of them feel they had to speak out.

"This should be a wake-up call to management and ministers alike. If the government dictates that we must reduce in size then they must reduce the workload accordingly or face the consequences for the justice system."

A Scottish Government spokeswoman said: "These are staff matters for the Crown Office and Prosecution Service which operates independent of ministers.

"Through our Making Justice Work programme, the Scottish Government is putting in place a range of reforms to modernise and improve efficiency within the criminal justice system, reduce bureaucracy and red tape, and speed up the handling of business in our courts for the benefit of all involved."