Nicola Sturgeon has said it “beggars belief” that the UK is unable to say what relationship it wants with the EU 18 months on from the Brexit vote.
The first minister’s comments come ahead of the publication of a Scottish government assessment on the impact of Brexit on Scotland’s economy.
She is adamant that Scotland remains in the EU single market and customs union.
The UK government accused the SNP of “trying to undermine the result of a democratic referendum”.
It has already ruled out staying part of the market after Britain leaves the European Union.
The customs union is the European Union’s tariff-free trading area, which imposes the same taxes on imports from certain countries outside the EU.
The single market also includes the free movement of goods, services, capital and people.
Ms Sturgeon said that so-called hard Brexiteers had failed to show how their approach would compensate for the loss of access to European markets.
She said: “More than 18 months on from the Brexit vote, it beggars belief that the UK government is not only still unable to say what kind of relationship it wants with the EU, but has also failed to produce any meaningful economic assessment of the different possibilities.”
Ms Sturgeon added: “There is zero credible evidence to suggest leaving the single market will bring any benefit to our economy. Indeed, as our analysis will show – the harder the Brexit the worse will be the outcome.”
The Scottish government’s paper, titled Scotland’s Place in Europe: People, Jobs and Investment, also details what it believes to be the benefits of the continued freedom of movement for workers from the European Union.
The Scottish Conservatives have urged Ms Sturgeon to back UK-wide rules on trade and immigration rather than seeking any separate deal for Scotland.
It follows the results of a UK-wide survey headed up by Sir John Curtice that suggested 59% of voters in Scotland backed an end to freedom of movement.
The UK government called on the Scottish government to work with it for the benefit of the whole of the UK.
‘Vital internal market’
A spokesman said: “We are seeking a deal that works for the whole of the UK, that delivers on the result of the EU referendum.
“Rather than trying to undermine the result of a democratic referendum, we urge the Scottish government to work with us to ensure, as we leave the EU, we protect the UK’s vital internal market.
“Scotland trades four times as much with the rest of the UK as it does with the EU, so it is vital that we ensure that market continues unimpeded.”
Meanwhile, Labour has been urged to join a cross-party bid to keep the UK in the single market and customs union.
The SNP, Liberal Democrats, Plaid Cymru and Greens have joined forces to back an amendment to the EU (Withdrawal) Bill when it returns to the Commons this week.
If passed, the move would stop ministers being able to use so-called Henry VIII powers to take Britain out of the single market and customs union.
The move follows a Brexit summit by the leaders of the four parties which Labour refused to attend.