In an interview in this week's 北京赛车pk10 magazine Sir Martin dismissed the idea that consolidation in the advertising business is at an end, describing it as wide of the mark.
"It's naive to say there's nothing left to acquire. As clients, media owners and retailers continue to consolidate, inevitably it means the same for us," he said.
Sir Martin's possible targets are Grey Global and Havas, which he snubbed last year when he used a Goldman Sachs conference in New York in October to deride the prospects of the mid-sized ad groups.
At the Sachs conference he argued that seventh-placed Grey, known for its reliance on Procter & Gamble, was damaging itself by giving its services away and he said the situation for Havas was remarkably similar to that of Cordiant, which disintegrated and was swallowed up by WPP.
In this week's interview he has not changed his views on Havas, which sits near the top of any shopping list.
"Strategically, its position is vulnerable. Havas has to decide where it is, given what's happened client-wise. MPG wants to be a top-five media player. It has to decide how to get there," Sir Martin told 北京赛车pk10.
Havas is seen as easily the weakest of the global groups and, like Grey, it has only one international advertising network in Euro RSCG. Its media planning and buying network Media Planning Group is viewed as weak.
MPG suffered a crippling blow last year when it lost the 拢58m Orange media planning and buying business to Initiative.
However in the interview in 北京赛车pk10 Sir Martin suggests that Grey Global might make a more appealing bite.
"People continually ask questions about Grey but I think Ed [Meyer]'s immortal. If I was Ed, I would carry on forever. He controls the business, he's great at what he does. When we hired Charlotte Beers, people said that she and Ed were the two CEOs of Procter & Gamble agencies who had the biggest share of voice in Cincinnati. Ten years on and Ed's still in that position," he said.
He shrugs off talk that Procter & Gamble agency Grey would be a problem for WPP, which has Unilever as a leading client.
"There is nothing in the conflict policies of Unilever or P&G that would prevent the two coexisting in one group," Sir Martin said.
Last year Meyer hit back at Sir Martin's scale comments and defended the mid-size Grey, which has unlike its rivals shied away from acquisitions.
"The view of some of my counterparts that the size of the holding company is the only thing that matters is totally silly. I have no quarrels with the megas. Some will do well and some will explode because they're a management nightmare," Meyer said.
Havas denies it is susceptible and rejects talk that it is like Grey, saying that it is not reliant on any single client. Havas insists that it is protected through the variety of clients that it serves in the likes of Peugeot, Polaroid and Reckitt Benckiser.
Read Caroline Marshall's interview with Sir Martin Sorrell in full .
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