THE prospect of a hard Brexit could lead to a second independence referendum by early 2018, the Scottish Green co-convener Patrick Harvie has predicted.

The Glasgow MSP said it was a “reasonable guess” that Scots would go to the polls again at the halfway mark of the Brexit talks, which are due to run for two years from March.

He said the trigger would be the UK government refusing to entertain Nicola Sturgeon’s request for a bespoke Brexit deal allowing Scotland to stay in the EU single market.

The First Minister this week ruled out a referendum in 2017, but said the option remained on the table in the longer-term to avoid Scotland being dragged over a “Brexit cliff edge”.

Asked about the timing, Mr Harvie, who supports independence, said it was vital to advance the SNP’s draft referendum bill through Holyrood in case it was needed next year.

He said: “I don't think anyone expected a second referendum to be held this year. What’s been very clear is that the option needs to remain on the table, and we support that.

"That means the legislation to allow Holyrood to make that decision has to be progressed this year."

He said it was “very hard to see through the mists of Brexit” at present, and attacked the UK government for its “lack of clarity” on the issue.

He said: “I think a reasonable guess at the moment might be that if Scotland chooses to have this question put again, if the UK chooses to dig its heels in and refuses to respect the way that Scotland voted to remain in the EU, then maybe at some point round about the halfway mark of the two-year Brexit negotiation period, or not long after that halfway mark, we might need to be in a position to put that question to the public.

"Because there is a contradiction between the 55 per cent vote in 2014 to stay in the UK and the 62 per cent vote last year [in Scotland] to stay in the European Union.

"I think we need to explore the options to see if both those votes can be respected, but if the UK Government refuses, if they refuse to budge from their hard Brexit, no special arrangements for Scotland position, then that contradiction will stand, and it may be that only the Scottish people are in a position to resolve that contradiction."

Mr Harvie also told BBC Radio Scotland his MSPs could not currently support the SNP’s draft budget for 2017-18 because its tax plans were not “progressive” enough, and it would inflict “astonishing” cuts on councils.

With the SNP two MSPs short of a majority at Holyrood, the government needs at least one other party to support it - or merely abstain - in order to pass the budget next month.

Mr Harvie said the government “needed to give some ground" and "move some way towards some other party" in negotiations in the coming weeks.

Asked if his party could support the budget as it stands, he said: “I don’t think we can support a budget that has such astonishing cuts to local government services - local services are the ones that people rely on day in day out. We need to be investing in those.”

The Greens’ reluctance to support the budget without radical changes suggests the SNP may end up relying on the LibDems to survive the budget vote.

LibDem leader Willie Rennie later gave a substantial hint that his party was looking for more money for education for a budget deal.

At First Minister’s Questions, he urged Nicola Sturgeon to reverse a £90m real terms cut in college funding and invest an extra £70m in closing the attainment gap.

Labour Europe spokesman Lewis Macdonald said: "A hard Brexit would be bad for jobs and would confirm once and for all that the biggest threat to the Union is actually the Tories.

"However, a second independence referendum is not the answer.”