The UK Government's chief negotiator in protracted talks over funding for Scotland's new powers has gone on holiday despite Holyrood's extended deadline looming in a week.
Chief Secretary to the Treasury Greg Hands is taking "a long-planned, short half-term break", a Treasury spokeswoman said.
Scottish First Minister Nicola Sturgeon's spokesman said the holiday at such a crucial time in negotiations over the fiscal framework for the Scotland Bill "beggars belief".
The Scottish and UK governments are in dispute over the adjusted formula for Scotland's block grant, with each side insisting their preferred formulas would be to the detriment of Scotland or the rest of the UK respectively.
Holyrood's Devolution Committee has demanded a deal ahead of its next meeting on February 23, when it will hear from Scottish Deputy First Minister John Swinney and Scottish Secretary David Mundell.
Mr Hands has been invited to Holyrood's Finance Committee the following day.
He is expected to speak to Mr Swinney on the telephone on Tuesday and has offered to return from his holiday "if the Scottish Government is willing to make a substantial move" in the negotiations.
The Treasury spokeswoman said: "The UK Government remains absolutely committed to implementing the Smith Agreement in full and in line with the no detriment principles.
"The offer we have placed on the table would have delivered more funding for the Scottish Government than the existing Barnett formula since devolution in 1999.
"From the outset our position on the fiscal framework has been clear - we stand ready to do a deal that is fair for Scotland and fair for the rest of the UK.
"The Chief Secretary is away for a long-planned, short half-term break with his family but has made clear that he is ready to return at any time if the Scottish Government is willing to make a substantial move.
"Negotiations are still ongoing and the Chief Secretary will be speaking with the Deputy First Minister today."
The First Minister's spokesman said: "This beggars belief.
"Having secured an extra week for negotiations, the Deputy First Minister offered to clear his diary to go to London on Monday and do whatever was required during this week to thrash out a deal.
"We now find out that the reason a Monday meeting was not agreed to is that the UK Government's chief negotiator has gone on holiday to France - before even having the courtesy to respond to the revised proposal submitted by the Scottish Government last week.
"It is time for the UK Government to decide if they are really serious about reaching a deal. Otherwise, they will stand accused of breaking their vow."
UK ministers have said repeatedly that they are not working to a deadline and will continue negotiations until a satisfactory framework is agreed.