The SNP has tabled a debate for tomorrow calling for an end to the detention of children in the controversial immigration removal centre in Lanarkshire.
The Scottish Labour leadership has consistently refused to respond to criticism about the centre because it comes under Westminster control - in spite of increasing unrest inside and outside the party about the way in which the centre operates, particularly in its treatment of children and families.
Elaine Smith and Cathy Peattie, both Labour MSPs, spoke out about the centre last weekend, and the Nationalists had hoped to split the Labour group by attracting them, and a number of other dissident Labour MSPs, to their view.
But at a private meeting of Labour MSPs yesterday afternoon, the few who had spoken out in favour of the Nationalists’ motion were told bluntly not to "dance to an agenda driven by the SNP".
The stark, no-nonsense message was spelled out by an MSP close to the leadership and was interpreted as a clear warning to any member not to vote with the SNP tomorrow. It is believed that about four MSPs will either do so or abstain, but the rest are now expected to obey the leadership and vote against the SNP motion.
However, there is still a danger that Labour might be defeated in the vote because it was not clear last night what the Liberal Democrats and the Conservatives were planning to do.
The debate on Dungavel is the first real test for Jack McConnell since he won the election in May and although defeat will not commit him to anything, it would give the Nationalists a major boost and represent a significant setback for Labour.
It is also the first debate since the election when the Labour Party will have to stand on its own, without the support of its Lib Dem coalition partners, because the Dungavel centre comes under asylum and immigration policy. This is reserved to Westminster and so the Liberal Democrats are not bound by the partnership agreement on reserved issues. The party MSPs were meeting last night to decide their position but it is likely that most will abstain on the SNP motion, leaving Labour needing the support of the Conservatives to stave off a defeat.
The Tories will not decide on their position until later today, when they have seen both the SNP motion and the Labour amendment.
However, they could support Labour, saving the First Minister from defeat.
The Scottish Labour leader has come under intense pressure to respond to the SNP motion personally but has decided to stay in the background, preferring to leave it to Margaret Curran, the minister for social justice.
It is understood that Mr McConnell believes that Ms Curran has shown herself to be one of the best debaters in the parliament, particularly when taking on the Nationalists.
The SNP motion is an extremely simple one, calling just for an end to the detention of children at Dungavel.
John Swinney, the SNP leader, said yesterday: "There is a clear consensus in Scotland opposed to children being locked up in Dungavel. What’s more, I have no doubt that the overwhelming majority of MSPs agree.
"I hope that MSPs of all parties will feel able to support this clear, unambiguous statement of principle.
"I particularly hope that Jack McConnell will recognise that it is time to break his silence."
The First Minister has found himself in a difficult position over Dungavel. He is not able to intervene or express an opinion because it comes under the remit of Westminster.
But there was private delight within Labour ranks over the wording of the SNP motion because it is focused entirely on children.
Labour speakers will argue that one of the central tenets of government policy on asylum seekers is not to split up families, and they will demand answers from the SNP on whether the nationalists would divide families by releasing children from Dungavel and how long they would keep them apart.
The debate is certain to be fiercely contested and the result of the vote will rest on how the various parties in the new-look parliament perform in their first real test.