Nicola Sturgeon is putting more pressure on Jeremy Corbyn to call a confidence motion against the UK government.
The first minister believes the motion could succeed, but is only guaranteed if it is raised by Labour.
The SNP leader says she is still considering bringing forward the motion, but is calling on Labour, as the official opposition, to raise it.
She believes it will, at the very least, "clarify Labour's position".
But the Labour leader has so far ruled out the move, which could trigger a general election, until he can be sure of winning the vote.
'Weak and unstable'
Speaking on the Sophy Ridge programme on Sky News, Ms Sturgeon said: "We think Labour should table a confidence motion and I said last week if it does so, then the SNP will support that.
"I think it is possible that a confidence motion right now could succeed. This is a government that is weak and unstable and is becoming more weak and unstable with every day that passes."
Ms Sturgeon said that even if the House of Commons motion was not successful, it would at least help clarify the position of Labour.
She said: "Labour's position is that it won't back a second EU referendum unless it has tried and failed to trigger a general election. But if it won't try to trigger a general election we are in this catch-22 position and it seems to me that Labour is as much a barrier to making progress on Brexit as the Tories are."
Ms Sturgeon said she would continue talking to other opposition parties.
A Labour Party spokesman told the BBC: "Labour will bring a vote of no confidence when it has the best chance of succeeding.
"We are looking at this on a day-by-day, week-by-week basis."
Nicola Sturgeon's call comes just a day after one of Jeremy Corbyn's own MPs called on the Labour leader to "come off the fence" and back another vote on EU membership.
'Break the impasse'
Ian Murray, the MP for Edinburgh South, said he believed a call for a second referendum - or People's Vote - could command a majority in the House of Commons if supported by the Labour frontbench.
Mr Murray told the BBC: "The Labour Party will have to come off the fence on that at some point pretty soon because I think what they're trying to do might be incompatible with what's available.
"There's a majority of MPs that would stop a no-deal scenario from happening so that could be taken off the table.
"I think we can get a majority around a People's Vote because we need to try and break the impasse between now and the 29th of March."
Mr Murray said cross-party talks in parliament were ongoing to try and push for another EU vote.