It comes amid reports this morning that the SNP Government is set to back plans for Scotland to join the European Economic Area (EEA) - as the rest of the UK leaves the EU.
Even if the EU were to agree to such a proposal - and there is no evidence it would - the proposal would ensure border restrictions being imposed between Scotland and the rest of the UK - where most of the country's exports are sold.
The Law Society of Scotland has also warned that membership of the EEA would mean still being subject to EU regulations - but without any "direct influence" over how they were set.
This would directly break one of Nicola Sturgeon's own "tests", set out in July, when she argued that she wanted Scotland to "have a say in shaping" regulations.
In response to the reports, finance spokesman Murdo Fraser said:
"This is dishonest spin from the SNP.
"They know full well the EU would not allow Scotland to have a separate deal in the first place when the precedent that would set would go directly against the interests of some member states.
"It's also important to spell out the consequences of this idea.
"If the SNP's plan is to back a 'Norway-style' deal for Scotland, separate to the rest of the UK, that would erect a hard border between us and England, our largest market and nearest neighbour.
"And, as legal experts have made clear, it would also mean having no say whatsoever in the EU regulations which would still apply to us.
"One of Nicola Sturgeon's grandly-titled 'five tests' was to ensure Scotland had a say in shaping the single market, not just being subject to its rules. So this plan would not just be bad for Scotland, it would even break her own test.
"We will solve none of the questions thrown up by Brexit by cutting ourselves off from our nearest market, which is four times as important to us as the European market.
"The bottom line is that Scotland's interests are best served by being part of one United Kingdom negotiation - so that we get the best deal for all of us.
"That's all the more necessary given that the European institutions want to negotiate with one United Kingdom.
"The Scottish Conservatives are therefore committed to doing all we can to ensure the Scottish Government, and all Scotland's key sectors, play an integral role in that UK wide process."