Scotland's economy would shrink by 8.5 percent if Britain leaves the EU without a deal, Scottish leader Nicola Sturgeon warned Monday as she pushed for Britain to stay in the European single market.

"There is no option short of EU membership that is as good as being in the EU," First Minister Sturgeon said as she presented an analysis of the economic impact of possible future ties with the bloc.

"This is about degrees of what does the least damage to our economy," she told journalists in the Scottish capital Edinburgh.

According to the new analysis, Scotland's GDP would plunge 8.5 percent by 2030 -- or 12.7 billion pounds ($17.5 billion, 14.3 billion euros) -- if no deal is reached with Brussels and Britain has to fall back on World Trade Organisation rules.

This compares to a 6.1 percent (9.0 billion) fall if a free trade accord is signed with the bloc, and 2.7 percent (4.0 billion) drop if the UK joins the European Economic Area and therefore stays part of the single market.

Sturgeon said the impact study served as "compelling" evidence that Britain should remain part of the single market, if it is not possible to stay an EU member as her Scottish National Party would like.

Scotland backed EU membership by 62 percent in the June 2016 referendum, compared to the overall British vote on 52 percent in favour of Brexit.

The SNP has previously pushed for a second referendum on Scottish independence from Britain, as a result of Brexit, and Sturgeon said Sunday a decision on holding another vote would be taken when the shape of the EU deal becomes clearer.

Sturgeon predicted a majority of British lawmakers would support single market membership, despite Prime Minister Theresa May ruling it out largely owing to its condition of continuing free movement of people.

But the Scottish leader argued the EU migration which comes as part of the single market rules is "essential to our future economic prosperity".

"Growing our population, and particularly our working age population, is perhaps the greatest national challenge that we face," she said.

- Scottish leader 'scaremongering' -

London and Brussels are due to move on to the next stage of Brexit negotiations this year, after achieving "sufficient progress" in December on a preliminary exit agreement.

Sturgeon accused the British government of a "reckless and irresponsible approach" in the negotiations so far, arguing London had entered talks with unachievable aims, and urged the government to put single market membership back on the table.

But the Scottish wing of the ruling Conservative Party accused the SNP of "scaremongering" with its study.

"No-one's doubting that Brexit will pose challenges, but it will bring opportunities too," said Scottish lawmaker Adam Tomkins.

The Conservative government is expected to be further challenged by the SNP over the management of areas such as fishing, which are currently governed through the devolved Scottish Parliament, as Britain prepares legislation to repeal EU laws.

Sturgeon said on Friday the SNP would introduce a bill to ensure Scotland retains the devolved powers after Brexit, in an attempt to avoid a Westminster "power grab".