Nicola Sturgeon has claimed Kezia Dugdale told her in private that Scottish Labour would drop its opposition to a second referendum on independence in the wake of last year's vote to leave the EU.
The unverifiable claim, which Dugdale strongly denies, was the standout moment of the final Scottish leaders debate ahead of Thursday's general election which, north of the border, has been dominated by the topic of independence.
Labour has previously been attacked by the Scottish Conservatives for being weak on its opposition to a second independence vote, with UK party leader Jeremy Corbyn saying during the campaign that another would be "absolutely fine".
Sturgeon's admission was immediately seized upon by the Scottish Conservative representatives in the media spin room at the debate in Glasgow, who claimed the "bombshell revelation" had destroyed Scottish Labour's campaign.
"I respect the fact that many people disagree with me on a referendum and independence," said Sturgeon, in reply to a question from Dugdale about dropping plans for another vote. "But I also believe that Scotland needs to have a choice at the right time in the future because of the consequences of not having a choice – that we may have to accept a disastrous Brexit."
Sturgeon added: "You [Dugdale] used to agree with me on that. You and I spoke the day after the EU referendum and you told me then that you thought the change with Brexit meant that Labour should stop opposing a referendum."
Scottish Conservative leader Ruth Davidson questioned Sturgeon further on the admission, with the first minister elaborating: "She [Dugdale] said that she thought Brexit changed everything and that she didn't think Labour could go on opposing a second independence referendum."
A senior SNP source told BuzzFeed News after the debate that Dugdale had previously spoke publicly about the conservation, but that she had missed out a "key part" when talking about it – the part which Sturgeon revealed tonight.
Dugdale strongly denied the claim as being "not true" and "complete nonsense" during the debate and, minutes after it ended, tweeted that it was a "categoric lie" and a sign of desperation on the part of the first minster.
Labour MSP Anas Sarwar told BuzzFeed News he thought the claim was just a "dead cat" – a term coined by the Conservative campaign in 2015 for a sensational claim to distract from other your own campaign's difficulties.
A spokesperson for Scottish Labour also accused the first minister of lying and said it was an "act of desperation" in the final few days of the election campaign, speculating that Sturgeon knows her party is declining in popularity.
“This is a lie from Nicola Sturgeon," said the spokesperson. "It is insulting and demeaning to the office of First Minister. It is nothing but a final act of desperation from an SNP leader who knows the public has turned against her. It shows how far she's prepared to go in the hope of electing a Tory government."
“Kezia Dugdale campaigned tirelessly against independence in the 2014 referendum. She's campaigned tirelessly against a divisive second independence referendum. The Labour party will never support independence because of the turbo-charged austerity it would inflict on working people in Scotland."
In the media spin room in Glasgow, Scottish Conservative MSP Adam Tomkins said: "This is a bombshell revelation, which holes Scottish Labour’s entire campaign below the water line. Kezia Dugdale has spent this campaign claiming she opposes a second independence referendum. Now we learn she’s been having private chats with Nicola Sturgeon about her support for it.
"It is an utter disgrace and it proves that the only pro-UK vote at this election is for the Scottish Conservatives."