How big a threat to Humza Yousaf is a no-confidence vote?

Scotland's first minister, Humza Yousaf, is facing a no-confidence vote after the collapse of his party's agreement with the Scottish Greens.

Mr Yousaf hopes to continue in power, leading a minority government at Holyrood, after deciding that the partnership with the Greens has "served its purpose".

But Scottish Conservative leader Douglas Ross has described him as a "lame duck" first minister and says he will lodge a no-confidence motion.

So what happens next - and how big a threat is this for Mr Yousaf?

In general terms, it is a formal expression from a decision-making body on whether officers or leaders are fit to continue in office.

The Scottish Parliament defines it as a motion that says some MSPs do not have confidence in a government minister, the first minister, or all Scottish ministers.

So in this case it is motion that will declare Mr Yousaf unfit to hold the office of first minister.

A motion of no-confidence requires the support of at least 25 MSPs.

The Scottish Conservatives have 31 MSPs so that seems guaranteed.

Members are usually given at least two sitting days notice of such a vote.

The Scottish parliamentary bureau won't meet until next week to schedule business, so it looks like Wednesday or Thursday would the earliest possible date.

If a majority of MSPs do not have confidence in the first minister, he would be expected to resign - although he is not obliged to do so.

In practice, it would be hard to continue in the role without the backing of parliament.

In the event that Mr Yousaf resigned as first minister, MSPs would have 28 days to elect a replacement.

If they failed to do so, it would lead to an election being called.

The SNP have 63 MSPs who can presumably be counted on to support Mr Yousaf and vote against the motion.

The Scottish Conservatives, Scottish Labour and the Scottish Lib Dems have 57 MSPs between them who will likely back it.

The Scottish Greens have also now announced their seven MSPs will back the no-confidence vote – so it all depends on the sole Alba MSP Ash Regan.

Ms Regan is a former SNP MSP who defected to Alba - which is led by Alex Salmond - after finishing third behind Mr Yousaf and Kate Forbes in last year's SNP leadership contest.

If she was to either abstain or vote in favour of the motion, it would be enough to see the no-confidence vote carried.

But if she sided with the SNP, it would result in a 64-64 tie.

In that scenario, the presiding officer casts a deciding vote, which by tradition is always for the status quo - meaning Humza Yousaf would win the confidence vote.

Ms Regan is therefore in a strong bargaining position to strike a deal with the SNP in return for her support.