Scottish Liberal Democrat leader Willie Rennie has promised his party's MPs will vote against giving Holyrood permission to hold a second independence referendum.
In an interview at his party conference in Perth, I asked Mr Rennie about the increasing prospect that First Minister Nicola Sturgeon will seek Holyrood's backing for 'indyref2'.
As constitutional matters are reserved to Westminster under the current devolution legislation, any new referendum would have to be approved by the UK parliament.
Mr Rennie told me:
The context for Mr Rennie's intervention is his speech to the conference this afternoon where he will make "a very positive, a very emotional case" for the Union.
He said he did not accept that there was going to be a second independence referendum.
His aim was to stop 'indyref2' "dead in its tracks before it happens". It was about "the ties that bind us across the UK".
Mr Rennie claimed the SNP 'never shut up about it" (independence) so the Lib Dems were going to "make the positive case back to them".
So I asked him will Lib Dem MPs at Westminster block that second independence referendum if the Scottish parliament votes for one?
Mr Rennie told me:
His remarks appear to contradict what his former party leader Nick Clegg told journalists at the conference yesterday.
According to today's Herald newspaper, Mr Clegg was asked if the UK Government should block another referendum by denying Holyrood the necessary legislative power under Section 30 of the 1998 Scotland Act. He said: “I think it would be very difficult for any government of any composition in London to try and impose a fatwa on any move towards a referendum, if that was something which was being pushed, however unwelcome that is."
In my interview I pressed Mr Rennie. If a majority in the Scottish parliament - the Greens and the SNP both support indyref2 - call for another referendum, and it has to be approved by Westminster, will his MPs will vote against it, the will of the Scottish parliament?
He replied: "We will vote against independence referendum because that's the platform that we stood on last May. We will be true to what we said... So they will vote at Westminster to block indyref2?" We will vote against it. I can't be any clearer."
Did he not fear there would be a huge backlash against his party. Would they not be accused of thwarting the will of the Scottish people? The Lib Dem Scottish leader said: "No, I think there would be a huge backlash against us if we went against what we said last May on the platform, throughout every constituency in the country that we would not vote for another independence referendum."
Sources at the Lib Dem conference this afternoon played down the apparent differences between Mr Rennie and Mr Clegg, the former Deputy Prime Minister.
They said Mr Clegg has been addressing the issue of a second referendum and Westminster's attitude in general terms and that the party's MPs would vote against it.
The Lib Dems only have nine Westminster MPs so the attitude of the Tory government will be crucial to the prospect of a second referendum. Theresa May has been pressed on whether her government would give Holyrood permission to hold a referendum if a majority of MSPs called for it.
Up to now the Prime Minister has refused to answer the question stating that she and her party do not believe there should be a second referendum as the issue was decided in the first referendum in 2014.
The SNP have responded with:
You can see my interview with Willie Rennie in a special edition of Representing Border bringing you the highlights of the Scottish Liberal Democrat conference at 11.15pm on ITV Border Scotland and on our website after that.