THERESA May and Nicola Sturgeon will have their first Brexit showdown in London on Monday October 24, MPs have been told, as it was suggested any transfer of additional powers from Brussels to Holyrood on the back of Britain leaving the European Union might not be automatic.

David Mundell, the Scottish secretary, confirmed that the first meeting of the Joint Ministerial Committee to discuss Brexit, involving the UK Government and the three devolved administrations, will take place in 12 days' time. The meeting is expected to take place in Downing Street.

Stressing how he had already had constructive meetings with Michael Russell, the Scottish Government’s spokesman on the Brexit talks, Mr Mundell said: “The First Minister and the Prime Minister will meet on October 24 and their engagement will be essential to achieving what we want: the best possible deal for Scotland.”

In April, George Eustice, the UK Government minister for farming, food and the marine environment, said that Brexit would strengthen Britain because it would mean “important powers, including most of those that the EU has over fishing, will be automatically devolved to the Scottish Parliament,” adding that the Scottish Government would have “unprecedented power in fisheries management".

During Scottish Questions in the Commons, Carol Monaghan, the SNP MP for Glasgow North West, asked on the back of Brexit which powers currently controlled by Brussels would the UK Government “commit to giving to Holyrood and which would be re-reserved to Westminster?"

Mr Mundell responded by saying it was “self-evident that, because the devolution settlements within the United Kingdom are predicated on the basis that the UK was a member of the European Union, then those devolution settlements will be changed by the United Kingdom leaving the EU and those will be matters, which will be subject to debate and discussion".

The SNP’s Patrick Grady asked the secretary of state to clarify if this meant currently devolved powers could be taken away from Holyrood.

"Will you categorically rule out that powers will not be re-reserved to this Parliament as a result of the decision to leave the European Union?" asked the MP for Glasgow North.

Mr Mundell replied: "No, what I can say is that no powers which are currently exercised by the Scottish Parliament will be re-reserved to this Parliament as a result of the United Kingdom leaving the EU."

Later during a debate on Brexit, Alex Salmond, the former First Minister, asked David Davis, the Brexit secretary: "Agriculture and fisheries are not reserved, therefore they are devolved. Unless the Government intends to change that position, it'll be automatic that agriculture and fisheries powers go to the Scottish Government."

Mr Davis replied: "This is an area where we have not addressed or talked to the devolved administration at all yet. We will do so before we get to bringing it back."