The move could see about 500 procurators fiscal walk out early next year.

Lawyers working for the Crown Office are, it claims, are paid £15,000 less than their Scottish government counterparts.

Allan Sampson, FDA Scotland national organiser, said: “This is a long-running dispute about pay in COPFS (Crown Office and Procurator Fiscal Service), which has fallen significantly behind other government departments.

“We’ve been telling Scottish ministers about this issue over pay parity for years. It’s been an issue for over a decade.

“There’s been some sympathetic words, but nothing has been done to address it and patience is now running out. We were told at the start of November they wouldn’t meet our request and that’s what has led us to this point.

“We’re asking our members if they would be willing to take strike action, and we expect they will say yes to that. If they do, we will move to a statutory ballot early in the New Year.”

Scottish Labour justice spokesperson Rhoda Grant said: “It is unfortunate that the pay dispute has reached this stage. The Scottish justice system and its lawyers have been under immense strain in the past months, with the court case backlog increasing week on week.

“In a week where Scottish ministers rejected a proposal from the Law Society for grant to help legal firms hit by court closures, this is potentially a double blow to our strained justice system.

“We urge the Scottish government to work together with the FDA Union to find a solution urgently.”

Scottish Conservative justice secretary Liam Kerr added: “The SNP is now presiding over a situation where lawyers are furious and feel undervalued. Ministers need to get round the table with the COPFS and sort this out now.”

A spokesman for COPFS said: “COPFS has an ongoing and constructive dialogue with unions and staff over pay and benefits.”