Nicola Sturgeon and John Swinney could be hauled before a powerful Westminster committee and forced to testify what they knew of the SNP embezzlement saga.

The Scottish Affairs Committee (SAC) has been asked to intervene after the First Minister refused demands for a Holyrood inquiry into the unanswered questions swirling round the Nationalists’ cash scandal.

Mr Swinney has rebuffed calls for a Scottish Parliament probe into how Ms Sturgeon’s husband Peter Murrell was able to fund a lavish lifestyle for the couple with £400,000 from the party’s coffers - even as members raised fears that cash may be going missing.

But opponents say there must now be full disclosure on what senior SNP figures knew and when and whether taxpayers’ cash was stolen.

After the First Minister point blankly refused to entertain the prospect of a Holyrood probe, Tory Shadow Scottish Secretary Andrew Bowie formally invited the influential House of Commons committee to hold one.

The SAC is able to mandate witnesses to appear before it to give evidence - which means the First Minister and Ms Sturgeon could be summoned to London to answer questions.

Mr Bowie wrote to committee chair Patricia Ferguson - a Labour MP and former Holyrood deputy presiding officer - and said: ‘The seriousness of this case extends well beyond the wrongdoing of just Mr Murrell.

‘The SNP has been the governing party in Scotland for many years, and its internal governance arrangements have direct implications for public trust in political institutions.

‘The mere possibility that taxpayer funds may have been implicated significantly heightens the public interest in this matter and strengthens the case for thorough parliamentary scrutiny.

‘Of particular concern is the position taken by the current First Minister, John Swinney, who has declined to support a further inquiry on the grounds that the police investigation is sufficient.

‘In the absence of a Holyrood-led inquiry, there is a compelling argument for Westminster scrutiny to ensure that the necessary questions are asked, and lessons properly learned.’

Holyrood committees have often been accused of giving SNP ministers an easy ride due to strong Nationalist representation in their membership.

But the Westminster system has more teeth and is notoriously unforgiving and adversarial when questioning witnesses.

The SAC is comprised of 11 MPs, but only one of them, Dave Doogan, is from the SNP.

There are six Labour members and two each from the Conservatives and the Liberal Democrats.

By Friday night, eight had lent their support to the possibility of investigating the SNP.

Among them, Tory MP Jack Rankin insisted Ms Sturgeon’s claims that she knew nothing of her husband’s crimes as they unfolded - including that she was rarely in the couple’s kitchen - should be tested.

He said: ‘Clearly, questions must also be asked of the ex-First Minister.

‘[Her comment that] “I don’t like cooking” ranks alongside Dominic Cummings saying “the beaches are closed” [when he broke Covid-19 lockdown rules].

‘This must be looked into, and it can’t be the SNP whitewashing its own homework. Just imagine what they would be saying if this were Boris Johnson’s wife.’

Another member, Labour’s Douglas McAllister, said the matter should be considered only after Murrell is sentenced.

But he added: ‘My preference is for the Scottish Parliament to hold an inquiry.

‘However, if John Swinney and the SNP continue to block this, then Westminster should step in.

‘As a member of the SAC, I am of the view that we should hold an inquiry to investigate the SNP’s use of public funds.

‘We can of course, as a committee, offer to hold a joint hearing - of both the Westminster Scottish Affairs Committee working with the Scottish Parliamentary Committee.

‘I would welcome that. Failing such, we must step in and investigate if Holyrood won’t.’

On Friday, Ms Ferguson said: ‘We are aware of calls for the Scottish Affairs Committee to undertake work in respect of the recent developments relating to the SNP party’s finances. The Committee will consider this issue in due course.’