DAVID Mundell’s position looked increasingly vulnerable last night after Theresa May refused to say whether she received representations from him on her controversial pact with the DUP.

The SNP’s Ian Blackford twice asked the Prime Minister in the Commons yesterday whether she had received “any representations from her Scottish Secretary” about the £1 billion deal to support her minority government “either before or after it was signed”.

It was Blackford’s first stint as the party’s Westminster leader at the weekly session of Prime Minister’s Questions since succeeding Angus Robertson, who lost his Moray seat on June 8. Blackford accused May of failing to “give a straight answer” and asked again: “Did she receive any representations about the DUP deal from the Secretary of State for Scotland – yes or no?”

May responded only that she “regularly” received representations from the from the Scottish Secretary about matters relating to Scotland, but failed to say whether any specific ones were made in relation to the DUP deal.

On Monday the May announced £1bn in additional funding for Northern Ireland as part of a “confidence and supply” agreement with the DUP to prop up her Government after the Tories lost their majority at the General Election.

The arrangement means the 10 DUP MPs will vote with the Conservatives on the Budget, the Queen’s Speech and Brexit legislation.

The deal was immediately condemned by First Minister Nicola Sturgeon who said that the bypassing of the Barnett formula, under which funding is distributed to the devolved parts of the UK, resulted in Scotland missing out on £2.9bn. Welsh First Minister Carwyn Jones also hit out, branding the deal “a straight bung” by May to cling on to power.

Blackford returned to the issue yesterday, pointing out Mundell had “insisted that Scotland would see increased funding if the DUP secured money for Northern Ireland as part of a confidence and supply deal”.

The SNP’s Westminster leader said May’s failure to give a straight answer “speaks volumes and has only succeeded in piling more pressure on the Scottish Secretary, whose position now looks less secure with every day that passes”.

The controversy also dominated Northern Ireland Questions earlier in the day in the Commons, with the SNP spearheading the attack.

Alison Thewliss led the criticism, saying DUP MPs were now worth more than footballer Cristiano Ronaldo. Thewliss underlined warnings made by Tony Blair’s former chief of staff Jonathan Powell, who played a key role in negotiating the Good Friday Agreement, that the deal could impact on the peace process as the UK Government could no longer be seen as a neutral player in Northern Ireland.

The SNP’s shadow spokeswoman on Treasury matters asked the Northern Ireland Secretary James Brokenshire: “Does the Secretary of State agree with Jonathan Powell that it is now impossible for the UK Government to be even-handed in Northern Ireland?”

Fellow SNP MP Patricia Gibson added: “Can the Secretary of State not see that the UK Government’s credibility with the other constituent parts of the United Kingdom has been destroyed following this £1.5bn bribe from Northern Ireland, subverting the rules of Barnett as the price of staying in office?”

Brokenshire rejected both suggestions, having earlier said that the Government would “continue to govern in the interests of all parts of the community and work in partnership with the Irish government”.

But shadow Northern Ireland secretary Owen Smith was sceptical.” He said: “I don’t doubt for a minute the good faith of the Secretary of State ... but he must acknowledge that his desire to look impartial has been compromised by the arrangements with the DUP.”

A spokeswoman for the Scotland Office said the Prime Minister had full confidence in the Secretary of State.