Plans for a raft of tribunals to be devolved to Scotland as part of the Smith Commission have been delayed for at least two years.

The Scottish Government was due to take over the operation of several reserved tribunals, including employment hearings, this year, but a report from Scottish Tribunals makes clear this will now not take place "before 2022".

Officials at Holyrood claimed it was "disappointing" that Westminster had not been able to publish its plans for the transfer five years on from the agreement.

However, a leading legal expert questioned why there had been no outcry from the SNP over the lack of progress.

The delay has also prompted concern from trade union activists, with some describing the situation as "completely unacceptable".

Dave Moxham, deputy general of the Scottish Trades Union Congress, said: "We're concerned at the length of time this has taken and we're certainly concerned that we haven't had any substantive contact from the Scottish Government on this issue for a significant period of time.

"We have now sought a meeting with the cabinet secretary for justice at which this is one of the major agenda items that we will be raising."

The transfer of tribunals was put in place as part of several measures designed to increase devolution following the 2014 Independence Referendum.

The Smith Agreement stated that "all powers over the management and operation" of reserved tribunals should be devolved to the Scottish Parliament. This is done via a draft order in council - a document which is drawn up by the UK Government. 

However, an initial draft of plans for employment tribunals faced a backlash from experts in the field, with trade unions, consumer groups, legal professionals and even employment judges raising concerns.

Mr Moxham added: "I think the issue is that they've not managed to convince the various stakeholders - consumer groups, trade unions, the judges - that they have a clear vision which is acceptable and implementable."

Trade Union Unite said it was also "deeply concerned" at the delay.

The union's Scottish secretary Pat Rafferty said: "In the context of Brexit and a Tory majority it’s an imperative that every tool is used by the Scottish Government to protect and safeguard workers, instead a power which has been devolved is not being used for reasons unknown which is completely unacceptable."

Patrick McGuire, a partner with Thompsons Solicitors, which represents several trade unions, added that questions need to be answered on the reasons behind the delay.

"If Westminster are creating this delay, where's the public political outcry?" he said. "We've certainly not seen any particular public pushing by the Scottish Government for it to be delivered. I've not seen questions being asked, I've not seen letters being sent, I've certainly not seen public pronouncements, so have they just forgotten about it?

"If it is down to the UK Government, then we come back to The Vow and false promises. If that's the case, the SNP should be shouting it from the rooftops, but we've not had that. So what is going on?"

A Scottish Government spokeswoman said officials are continuing to work with the UK Government to fulfil the commitments of the Smith Commission. 

She added: "It is disappointing that after five years the UK Government have not been able to publish its proposals for how this devolution will be delivered and we have written to them seeking progress.

“We are optimistic a way forward can be agreed in the near future, although we are clear that the original proposed transfer date is no longer viable. We will seek to agree a realistic transfer date as part of our current engagement."

An HM Courts and Tribunals spokesman added: "This is a complicated and detailed piece of work with good progress being made."

HMCTS declined to comment on the reasons behind the delay.