The chair of a senior parliamentary watchdog is demanding an investigation into Downing Street's talks with Nissan.
The Prime Minister hosted Nissan boss Carlos Ghosn in October ahead of the decision by the automaker to continue to manufacture its new Qashqai in Sunderland.
Ministers have since denied that any special offer was made to the firm to secure development in the North East, but Treasury Select Committee chair Andrew Tyrie has now asked the National Audit Office to investigate.
As part of its forecasts for the Autumn Statement, the Office for Budget Responsibility last week declared that while it had asked the government whether its talks with Nissan had generated any contingent liabilities, "the Treasury declined to address the substance of our question".
Tyrie's own inquiries saw chancellor Philip Hammond write a letter to the Treasury committee chair earlier this week, but in a committee hearing yesterday, OBR chief Robert Chote noted that Hammond's reassurances seem to reference only the view of Greg Clark's business ministry.
And Chote pointed out Hammond's letter also noted that any expenditure arising from the Nissan talks would fall "within existing DEL [Departmental Expenditure Level] totals".
"One thing it does imply is that the commitment could incur a cost, otherwise that point would not have been mentioned. So that would be one thing to conclude," Chote said.
"The other point, presumably, is that they assume that if there are costs, they are sufficiently modest that they could be incorporated within the DELs without having to draw on the reserve or do something more dramatic."
In a statement issued this afternoon Tyrie said: "The chancellor has not answered the crucial question: whether an assurance was given to Nissan which could constitute a contingent liability, or support consistent with the provisions of the Industrial Development Act 1982.
"So I have written to Sir Amyas [Morse] asking him to examine whether contingent liabilities have arisen as a result of government commitment and/or assurances made to Nissan."