The head of the civil service has been urged to step in and stop the Scottish Government planning for an independent Scotland.

Nicola Sturgeon announced in the Programme for Government last year that civil servants would resume work on a plan for how Scotland would look outside the UK.

It emerged this week that 11 civil servants have been tasked with creating the prospectus.

On Sunday, shadow Scotland secretary Ian Murray wrote to Cabinet Secretary Simon Case – the ultimate head of the civil service in the UK – calling for an investigation that will “ultimately reverse” the decision.

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“Many would consider this is a deeply inappropriate use of public funds at any time, but not least while Scotland is still in the midst of a pandemic, when energy bills are rising and families’ household budgets are squeezed,” the letter said.

“The Scottish National Party is of course perfectly entitled to set out its plans for separation, but Scottish taxpayers should not be expected to foot the bill for a prospectus which the majority have already rejected in a national referendum.

“I consider this to be an inappropriate and entirely wasteful use of taxpayers’ money and hope that you will investigate and ultimately reverse this decision.”

A spokesman for the Scottish Government said: “It is the role of the civil service to support the elected government of the day in developing and implementing its policies.”

This view was supported by former Tory MSP and constitutional law professor Adam Tomkins.

“I’m not in favour of Scottish independence and I’d much rather see a Scottish Govt with very different priorities, but I don’t understand this,” he said on Twitter.

“Civil servants exist to support their ministers and, like it or not, it is Scot Gov policy to pursue indy via a second indyref.”

Prof Tomkins added: “Muscular unionism was stupid, self-defeating and rightly abandoned when Whitehall flirted with it last year. It’s equally stupid and self-defeating when pushed by folk who should know better such as Ian Murray MP.”

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A spokesman for the Cabinet Office refused to be drawn on the substance of the letter, but said: “The UK Government is clear that now is not the time for a further independence referendum.

“Our collective priority must be responding to and recovering from the challenges the Covid pandemic has created, rather than constitutional debates.”

The prospectus will replace the independence White Paper that was published before the 2014 referendum, which laid out the various policy positions that would be put in place in an independent Scotland.