A separate Brexit deal for Scotland is "not a realistic prospect", the Chancellor has said.

Philip Hammond also reiterated the UK Government's position that it will be Downing Street alone that negotiates with the European Union, not the devolved administrations.

Hammond's comments on Brexit came in a briefing to journalists which STV News was not allowed to film.

The Treasury earlier rejected STV's requests for an interview with the Chancellor.

Instead the Treasury offered to do one broadcast interview to be used on a shared basis.

The comments come just weeks before the Scottish Government will put forward proposals to ensure Scotland remains in the European single market even if the rest of the UK does not.

Nicola Sturgeon has said her government's proposals to Downing Street will include devolving immigration to the Scottish Parliament.

The Chancellor called a devolved immigration system "impractical".

Hammond said: "I honestly think this is not a realistic prospect. The European Union is clear it will negotiate a deal with the United Kingdom. The United Kingdom is a member state.

"I think you have to only think about it for a few moments that a separate to realise that a separate immigration deal for any part of the United Kingdom would be impractical.

"I know Scotland, like the rest of the United Kingdom, has important trading relationships with the rest of the European Union but Scotland"s most important trading relationship is with the rest of the United Kingdom.

"That is four times more important to Scotland than its trading relationship with the rest of the European Union and it is not at all clear how being outside of the UK's arrangements with the European Union could in anyway advantage Scotland."

He added: "I would suggest it would be a disadvantage overall to Scotland.

"I don't hear that said often enough in the debate with Scottish colleagues over the European Union.

"While of course access to European markets is very important access to the rest of the UK market is far more important to Scotland."

The First Minister's office, however, said the Chancellor told the First Minister later on Thursday that Downing Street will consider her proposals "fully.

A spokesman for the First Minister said: "The Chancellor said he looked forward to hearing our proposals on Scotland's place in Europe, and that they will be considered fully by the UK Government - in line with the specific undertaking given to the First Minister by the Prime Minister when they met in Edinburgh in July.

"Those proposals, which we will publish in the coming weeks, will be aimed at securing Scotland's place in the single market, which is vital for jobs, investment and our overall economic wellbeing."

The Chancellor refused to be drawn on the prospect of the Scottish Parliament getting a say on triggering Article 50 while the process is subject to a live court case.

He did, however, call on the devolved government to stop being "backward looking" and "clutching at straws".

Hammond said: "I want to work closely with the Scottish Government and the other devolved administrations to make sure that we approach these negotiations in a way that secures the best possible deal for all part of the United Kingdom.

"I look forward to us moving on from this sort of slightly backward-looking, clutching at straws, trying to resist the will of the people, to embracing it, recognising it is going to happen and committing to work together to make sure it is done in a way that is most supportive of the UK economy and the Scottish economy."

In response to the fact Scotland voted to remain, unlike the UK as a whole, the Chancellor added: "This is a United Kingdom issue and the will of the people of the United Kingdom was to leave and we are clear that we cannot have a different deal or a different outcome for different parts of the United Kingdom.

"We have to work together as the United Kingdom now to get the best possible deal with Europe and then to make our way in the world to the benefit of all parts of that United Kingdom."

The Chancellor also echoed comments from the Brexit minister David Davis that the UK could pay money to the European Union even after leaving.

He said: "You can't go into any negotiation expecting to get every single objective that you set out with and concede nothing on the way.

"David Davis is absolutely right not to rule out the possibility that we might want to contribute in some way to some form of mechanism."

On a visit to Dublin on Tuesday, the First Minister questioned the Prime Minister's authority to take any part of the UK out of the single market.

Sturgeon said: "Scotland believes the UK as whole should now seek continued membership of the European single market and the European customs union.

"After all, 48% of voters choose to remain in the EU. So too did two of the four nations of the UK.

"And many people who campaigned to leave the European Union were clear in their view that doing so need not involve leaving the single market.

"So I accept there is a mandate for the UK Government to take England and Wales out of the EU but I do not accept there is a mandate to take any part of the UK out of the single market especially when we consider the economic consequences of such a step."

The Scottish Government has been contacted for comment by STV News.