UNIONIST parties should have the “courage of their convictions” and call another vote on Scottish independence, Scottish Greens co-leader Lorna Slater has said.

Last week, the UK Supreme Court ruled the Scottish Parliament did not have the power to legislate for an independence referendum.

The result means the UK Government would have to provide the necessary powers through a Section 30 order. 

In a joint interview with Patrick Harvie, Slater told the PA news agency that Unionist parties are scared of losing another referendum.

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“I’m continually frustrated by the Unionist parties lacking the courage of their convictions”, she said.

“Because I fully believe the reason they won’t let us have a referendum is because they know they’re going to lose it.

“They don’t spend any time at all arguing for why the Union is good, they know they haven’t got a basis for that – especially with Brexit, especially with unpopular things like the unelected House of Lords, especially the economic disaster we’ve seen coming out of Westminster.

“They know they have no case to make for the Union.”

It is also for the UK Government, Slater said, to lay out the path to a Section 30 order being granted.

“If this is a democracy, they have to say what the route to a Section 30 looks like,” she said.

Greens co-leader Patrick Harvie also said that a win in a de-facto referendum should mean the UK Government agrees to begin negotiations on Scotland’s separation from the union.

“I think the notion has to be that if every route to a referendum has been closed off by the UK Government, then you’re contesting an election on the basis that will establish the view of the Scottish people,” he said.

“If there’s a majority of votes cast for pro-independence candidates, that should begin the negotiations between the two governments.”

Slater added: “That highlights why a Section 30 is still the right route for this, because that’s the tool for having this discussion, it’s ridiculous to withhold that tool.”

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Senior SNP member Toni Giugliano – the party’s policy development convener – said at the weekend the promise of a section 30 order and a new referendum would “honour democracy”.

In response to Slater, Scottish Tory constitution spokesman Donald Cameron said "it takes some nerve" for a Green politican to refer to political opponents lacking "courage of their convictions".

He added that it was "nonsense to argue that the Conservatives have no case to make for the Union".