THERESA May has refused to say if Holyrood will make decisions over Scotland’s fisheries and agriculture after Brexit.

Though Tory Secretary of State for Scotland, David Mundell, had earlier offered an “absolute guarantee” that the Scottish Parliament would have more powers when Britain leaves the EU, his boss declined to make the same commitment.

And according to a report in The Times, a senior Whitehall source dismissed vows made by the Vote Leave campaign to Scots during the EU referendum as “another failed Michael Gove promise”.

During Prime Minister’s Questions, the SNP’s deputy leader, Angus Robertson, asked for a commitment that powers over those areas currently held by Brussels would be handed back to the Scottish Government rather than the UK Government when Britain leaves the EU.

The Prime Minister said the “overriding aim” for her government was to “ensure that we do not damage the important single market of the United Kingdom”.

Robertson said those working in the agriculture and fisheries sectors in Scotland “were told during the Brexit referendum that farming and fisheries powers would be exercised fully by the Scottish Government and the Scottish Parliament”.

He added: “Judging by the Prime Minister’s answer, however, it seems that that will not be true. Will the Prime Minister confirm today — she has the opportunity — that it is her intention to ensure that UK ministers will negotiate and regulate over large areas that impact on Scottish fisheries and agriculture post-Brexit?”

The Prime Minister replied: “We are in the process of discussing with the devolved administrations the whole question of which of the powers that currently reside in Brussels will be returned and will remain at a UK level for decisions and which powers will be further devolved to the devolved administrations. That is the discussion that is taking place at the moment. He asks about the Brexit negotiations with the European Union, and it will be the UK Government that will be negotiating with the European Union, taking full account of the interests and concerns of the devolved administrations and, indeed, of all the regions of England.”

During the EU referendum, Tom Harris, the former Labour MP who led the official Scottish Vote Leave campaign, told reporters at its launch that Scotland would have far more freedom to control fisheries and farming without interference from London after Brexit.

Standing alongside pro-Brexit Tory MSPs, Ross Thomson and Graham Simpson, Harris said: “We’ve seen the decimation Brussels has caused our fishing and farming communities, and if we want more powers for the Scottish parliament to create better policies, it’s time to vote leave.”

Yesterday, a Whitehall source told The Times, that the offer was “another failed Michael Gove promise” and that there was no “firm commitment”.

Though the paper said the Government was “willing to work with the Scottish Government over which powers would return” and were “sympathetic to the broad arguments”.

During her speech to the David Hume Institute on Tuesday night, Nicola Sturgeon has raised the spectre of a Holyrood power grab by the Tory government, accusing them of undermining devolution.

“It is clear from their statements that even elements of farming and fishing policy — which have been a wholly devolved competences from day one — now risk being taken back to Westminster,” she said.

After that speech, Tories lined up to accuse the First Minister if scaremongering.

Murdo Fraser tweeted that Sturgeon was showing “increasing signs of hysteria and detachment”.

Earlier in the day, David Mundell has offered an “absolute guarantee” that Holyrood would be given greater control over Scottish affairs after Brexit. Speaking during Scotland Questions in the Commons, Mundell said: “This Government’s plan is to engage with the Scottish Government and with the other devolved administrations to discuss these very serious issues.

“It’s not to go out and tell the people of Scotland that the devolved settlement is being undermined by Brexit — a Brexit which will lead to more powers being exercised by the Scottish Parliament.

“I can give you an absolute guarantee that after the United Kingdom leaves the EU, the Scottish Parliament and Scottish Ministers will have more powers than they have today.”

Theresa May travels to Scotland tomorrow to make a speech at the Scottish Tory conference in Glasgow.