(Adds comments from Sturgeon, background)
EDINBURGH, Jan 15 (Reuters) - Scotland will suffer an 8.5 percent hit to the size of its economy by 2030 if Britain leaves the European Union with no trade deal, the Scottish regional government said as it upped its calls for Britain to stay in the EU's single market.
Business investment in Scotland could fall by up to 10.2 percent, compared with continued membership of the EU, in the event of no Brexit deal, the devolved Scottish government said in an economic impact assessment published on Monday.
Scotland's first minister Nicola Sturgeon, who campaigned hard against Brexit, said Britain remaining in the EU's single market, if not the bloc itself, was now the best realistic option. But it would still hurt Scotland.
"If Brexit is to proceed then staying in the single market is the only option that makes sense," she told reporters.
Staying in the single market as a member of the European Economic Area would mean Scotland's economy would be 2.7 percent smaller by 2030 than it would be if Brexit did not happen at all, Sturgeon said.
"None of these options are as good as staying within the EU," she said.
Scotland's economy represents less than a tenth of Britain's economy as a whole.
Voters in Scotland voted to remain in the EU in the June 2016 Brexit referendum. But UK voters overall backed leaving.
Monday's report said the only credible outcome of the Brexit negotiations between Brussels and London due to take place this year was for Britain to be a member of the EEA.
However, Prime Minister Theresa May has ruled out Britain becoming part of the EEA which would involve continued unrestricted freedom of movement of workers from the EU into Britain, something May has vowed to end.
Opposition Labour Party leader Jeremy Corbyn has also said Britain should leave the single market. But Sturgeon said she believed his position could be changed if there was enough opposition from within Labour. (Reporting by Elisabeth O'Leary; Editing by William Schomberg)