The row over the Tories’ £1billion deal with the Democratic Unionist Party intensified last night as the SNP called into question David Mundell’s position as Scottish secretary.
His new Scottish colleagues also came under pressure from the nationalists to vote down the agreement.
SNP Westminster leader Ian Blackford insisted failure to do so would be the “final proof they do not stand up for Scotland” and make it “untenable” for Mr Mundell to continue.
However, a Number 10 spokesman insisted the prime minister had “full confidence” in him.
And West Aberdeenshire and Kincardine MP Andrew Bowie confirmed the 13-strong Scottish Tory group would not be withholding support.
It emerged earlier this week that Scotland will receive no extra money as a result of the confidence and supply arrangement, which has been described by Welsh First Minister Carwyn Jones as a “straight bung to keep a weak prime minister and faltering government in office”.
Nicola Sturgeon also hit out at the move, which she said showed the Tories would “stop at nothing to hold onto power”, and claimed Scotland would miss out on an estimated £2.9billion for public services.
Her intervention came after comments by Mr Mundell that he would not support “anything that could be construed as back-door funding” to Northern Ireland.
Yesterday, the SNP kept up pressure on the UK Government, posing a series of questions, including whether the Scottish secretary or Scottish Conservative leader Ruth Davidson had lobbied behind the scenes for more funding to come to Scotland.
Meanwhile, the Scottish Government has threatened to invoke formal dispute resolution procedures.
Scottish Finance Secretary Derek Mackay said it was “unacceptable” for the funding not to be subject to the Barnett formula, used to calculate public expenditure allocated to the devolved nations.
Mr Blackford added: “Either Mr Mundell has gone back on his word and agreed to the deal, or he has been left out of the loop and been utterly humiliated.
“He and Ruth Davidson must now get Scottish Tory MPs to vote down the deal – if they don’t, it will be the final proof they do not stand up for Scotland and that it is untenable for Mr Mundell to continue as Scottish secretary.”
A Number 10 spokesman said the DUP agreement had the “unanimous support of the cabinet”.
He added: “It was discussed at Tuesday’s cabinet meeting, where ministers congratulated the chief whip and first secretary of state for concluding a successful negotiation with the DUP.
“The prime minister of course has full confidence in the Scottish secretary.”
Mr Bowie argued the deal was about bringing stability to the UK and did not subvert the Barnett formula in any way.
Nor was the step unprecedented, he added, pointing to previous Northern Ireland support packages.
He said: “This is quite clearly not back-door funding.”
Labour claimed its research showed the rest of the UK could be being denied some £68billion.