David Cameron has repeatedly failed to confirm he did not talk to tobacco lobbyist Lynton Crosby about the coalition's decision to drop its plain packaging plans for cigarettes.
The prime minister subtly changed his language on the question of whether Crosby, who works one day a week advising the Conservative party on its general election strategy, had used his contact with Cameron inappropriately.
Cameron had previously denied Crosby had lobbied him outright. But in an interview conducted on Friday and broadcast this morning he refused to say he and Crosby had never discussed the issue.
"He's advising the Conservative party on how to take on Labour, how to make a political argument - not on policy, not on issues," Cameron told BBC1's The Andrew Marr Show.
"He doesn't intervene on those... He has not intervened in any way on this or indeed on any other issues."
Cameron said the government remained interested in plain packaging and claimed, astonishingly, that "we haven't changed our policy".
"There are merits to plain paper packaging - we're not going ahead with it right now but I certainly don't rule it out," he added.
"The whole thing from start to finish is something of a media invention."
The Labour party disagreed, warning that Crosby's "fingerprints are all over government".
It noted the prime minister's failure to issue a clear statement that he had not spoken to Crosby about plain packaging three times and has now released an interactive online timeline showing the full extent of his influence over the coalition.
It brings together reports about a secret Chequers summit between Crosby and Cameron with the government's U-turns on minimum alcohol pricing and the plain packaging issue.
"It's time for the prime minister to stop dodging the question and come clean about what conversations he's had with Lynton Crosby," the Labour party's vice-chair Michael Dugher MP said.
"If he doesn't, the impression will be left that this is a government led by an out-of-touch prime minister who promised change but is someone who can always be relied upon to stand up for the wrong people."
Shadow health secretary Andy Burnham has written to Cameron citing an allegation that Crosby signed a contract between tobacco firm Philip Morris International and his own firm Crosby Textor worth "in the region of £6 million".
Media reports on Friday suggested Crosby intends to drop his extra-curricular work in January until after the 2015 general election.