The Government has sought to play down suggestions Britain will be unable to remain in the single market after it leaves the EU after a memorandum carried by a senior Conservative Party aide suggested it was "unlikely".
Ministers faced fresh accusations that they had no strategy for Brexit after a long-lens camera in Downing Street caught the handwritten note which read: "What's the model? Have your cake and eat it."
The memo – which refers to some of the likely difficulties to arise during the negotiations - was being carried under the arm of an aide to Tory vice-chairman Mark Field as they emerged from a meeting with the Department for Exiting the EU at 9 Downing Street.
A government spokesman said: "These individual notes do not belong to a government official or a special adviser. They do not reflect the Government's position in relation to Brexit negotiations."
However Liberal Democrat leader Tim Farron said the memo appeared to reflect a government in disarray over the forthcoming negotiating process.
"If this is a strategy it is incoherent. We can't have our cake and eat it and there is no certainty on the single market. This picture shows the Government doesn't have a plan or even a clue," he said.
The memo includes a series of observations on the problems likely to arise once the Government begins the formal two-year process of EU withdrawal with the triggering of Article 50 in the early part of next year.
"Difficult on article 50 implementation - Barnier wants to see what deal looks like first," it noted in a reference to the lead EU negotiator Michel Barnier.
"Got to be done in parallel - 20 odd negotiations. Keep the two years. Won't provide more detail. We think it's unlikely we'll be offered Single Market."
The note appears to suggest a transitional arrangement which would allow the UK continued access to the single market after Brexit while it negotiates a new trade deal is also unlikely, despite Theresa May's assurance to the CBI left that business would not be left to fall off a "cliff edge".
"Transitional – loath to do it. Whitehall will hold onto it. We need to bring an end to negotiations," it said.
It also suggests that a deal on manufacturing should be "relatively straightforward" but admits that services were likely to prove harder.
The aide carrying the note was identified in press reports as Mr Field's chief of staff Julia Dockerill.
She is the latest in a growing list of visitors to Downing Street to be embarrassed after documents they were carrying were picked up by the cameras.
The exact significance of the comments is unclear – although that is unlikely to stop speculation on the implications, given the lack of publicly announced detail about the Government's negotiating strategy.
Mr Field does not have any official role in the negotiations but, as the MP for the Cities of London and Westminster, he is likely to take a close interest in the impact on the City.