Lynton Crosby is expected to drop his work for private firms, amid a continued row over whether he convinced David Cameron to drop plans for plain cigarette packs.
The prime minster has repeatedly said that he was not "lobbied" by the election guru on the issue, but he refuses to answer questions about whether they discussed it.
"I’ve been very careful to say what I’ve said which is that [Lynton Crosby] hasn’t lobbied me on any of these issues," he said again yesterday.
The careful use of the distinction between 'lobbying' and 'conversation' has not escaped Labour's notice.
"At least 12 times he has refused to give a straight answer," Jon Trickett, shadow Cabinet Office minister, said.
"It's astonishing the prime minister won't be clear about what conversations he has had with a man who is being paid by a big tobacco company at the same time as he is being paid by the Conservative party.
"The prime minister needs to stop taking the public for fools, and start being straight with people. If he has never had a conversation about tobacco policy with Lynton Crosby, he should just say so. If he has, then he needs to stop dodging and admit it right now."
Media reports this morning suggest Crosby intends to drop his extra-curricular work in January until after the 2015 general election.
The strategist is expected to work exclusively for Cameron in the last 15 months or so of the campaign.
Cameron made an effort to turn the tables back on Labour yesterday by comparing the Crosby row with Tony Blair's private operations.
"Tony Blair is someone who does lobby me from time to time on things like the Middle East peace process," the prime minister said.
"Do I have to know who all Tony Blair's other clients are? If I did that, I don't think I've got enough paper in my office to write them all down on."
That comment earned a stern rebuke from Blair, who has typically gone out of his way to be polite about his successor in public.
"Tony Blair does not 'lobby' David Cameron," a spokesperson said.
"You cannot seriously compare Tony Blair's role as quartet representative, which requires him to talk to governments around the world about the Middle East peace process, to that of a lobbyist."
A lobbying bill was published by the government this week, but it earned poor reviews on all sides of the debate.