SNP ministers are under fire for delaying their role in new devolved welfare powers, despite regularly criticising the Tory government’s approach and demanding rapid change.

It emerged yesterday that the Scottish Government had asked the Department of Work and Pensions (DWP) to stay in charge of delivering several benefits until 2020, even though Holyrood will be able to legislate on them next year.

The arrangement, known as “split competence”, means MSPs will acquire “legislative competence” over the benefits in 2017, in time for the SNP’s forthcoming Social Security Bill.

However SNP ministers will only acquire the “executive competence” for putting any changes into practice three years later, leaving it to the DWP in the interim.

Minutes of October’s joint ministerial committee on welfare reform between Edinburgh and London call the approach “untested”, “novel” and “new terrain for both governments”.

The delay is is in spite of the SNP routinely attacking the DWP for failing claimants.

Only last week, MP Margaret Ferrier condemned “the shameful delay in dealing with complaints at the DWP”.

The 2016 Scotland Act means a series of welfare responsibilities will be transferred to Holyrood, accounting for £2.7bn a year, or 15 per cent of the total Scottish benefit bill.

In what has become known as Tranche 1, MSPs and Scottish ministers will get powers over aspects of universal credit and employment support next year.

But Tranche 2, involving disability benefits, carers’ allowance, industrial injury payments and maternity, funeral and heating expenses, will be subject to the “split competence” timetable.

The minutes record SNP social security secretary Angela Constance described Tranche 2 as “more complex” than Tranche 1, and that with benefit recipients the main priority, “the group discussed that a suitable time period might be two or three years”.

Scottish Secretary David Mundell called the approach "pragmatic", but the group also noted “there was a significant and untested legal process to split competence”.

Tory welfare spokesman Adam Tomkins criticised the SNP for failing to tell Holyrood’s welfare committee about the plan.

He said: “This shows once again the SNP is a party which prefers complaining to governing.

“They demanded welfare powers at Holyrood, now they seem terrified of getting on with it.

“The unique split competence approach appears to be code for Scottish Ministers wanting to slow down the transfer of devolved welfare powers.”

Labour’s social security spokesman Mark Griffin said: “The new powers coming to our Scottish Parliament give us the opportunity to build a Scottish welfare state with dignity at its heart.

“There should be absolutely no delay in seizing that opportunity.”

Scottish LibDem leader Willie Rennie said that after the SNP had talked up a social security based on fairness and respect it was “frustrating that they are now dragging their heels“.

He said: “The SNP is constantly demanding new powers but seems curiously reluctant to use them. Perhaps this confirms they are more interested in independence. This also makes a mockery of the SNP’s claim it could set up a whole new country in just a few months.”

A Scottish Government spokeswoman said: “Our aim has always been a Scottish agency delivering devolved benefits by the end of this Parliamentary term, and that remains the case.

“Our priority is the safe and secure transfer of social security powers to Scotland so that we can ensure that everyone who relies on the benefits to be devolved will receive them at the right time and in the right amount. We will not risk anyone falling through gaps.”