SO, is there a smoking gun or at least a smoking cigarette?

Boris Johnson dismissed the row over Lynton Crosby's 
 relationship with David Cameron as a "storm in a teacup" while Ed Miliband accused the Prime Minister of "disgraceful behaviour" and demanded a top-level inquiry into whether he had compromised himself with big tobacco.

Now Mr Crosby, an Australian who helped the London mayor get re-elected, is Mr Cameron's election guru with Tory HQ having secured the services of his lobbying company.

Of course, coincidences happen in life and the fact Crosby Textor has campaigned Down Under against minimum alcohol pricing and plain tobacco packaging should, we are told, not lead anyone to have the slightest suspicion that Mr Crosby lobbied the PM to get these two issues dropped from the Coalition agenda.

At the end of last week this curious affair got curiouser when, after Chancellor George Osborne effectively announced the start of a shale gas revolution in Britain with generous tax breaks, reports emerged that Mr Crosby's company allegedly had, would you believe, links to the fracking industry. Tory HQ has insisted the Crosby row is "a red herring" produced by Mr Miliband, who wants to divert attention from his little difficulty of claims of vote-rigging in Falkirk.

Yet for all his high-flown claims of transparency, the public will suspect something is amiss when the PM continues to answer a question different from the one being put to him. That is, did he have a conversation with Mr Crosby about plain tobacco packaging? The PM's refrain is his Australian friend did "not lobby" him.

He was at it again yesterday. When repeatedly asked the question if he had talked to Mr Crosby about banning plain cigarette packaging, Mr Cameron came up with a new form of words, insisting the election strategist had "not intervened".

In defending his position last week, Mr Cameron let slip that one person who "does lobby me from time to time" was none other than Tony Blair. The ex-PM denied this. His aide 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."

So one man's conversation is another man's lobbying, it would seem. Which is the nub of the Crosby affair.

One interesting development in the furore is that Tory HQ has made clear the "Wizard of Oz" will become a full-time adviser in No 10 and stop advising other clients by the end of the year.

"The questions about his other clients will become a feature of the past," one source insisted. This clearly suggests Mr Cameron recognises the Crosby row is damaging and is trying to neutralise it as much as possible in the run-up to the General Election.

The PM has sought to take the moral high ground on lobbying with the publication of the Lobbying Bill.

Given politics infects everything, it should come as no surprise Mr Cameron decided to tag on to the plans for a lobbying register, moves to tighten up rules on strikes and union funding of Labour. As someone somewhere once said – it could even have been Mr Crosby – every crisis is an opportunity.