Robert Lerwill, the chief executive of Aegis, was ousted unexpectedly yesterday after a boardroom falling-out that reignited hopes of a tie-up with Havas, a rival advertising group.

Mr Lerwill is understood to have fallen out with John Napier, the chairman, and will leave at the end of the month after nearly four years at the helm. He will be eligible for a payoff worth about £1 million.

In a carefully worded statement, Mr Napier said that Aegis needed to be “in the best possible shape to meet the challenging conditions ahead” after a three-month period in which the shares had halved amid a faltering performance from the group’s US market research business.

Mr Lerwill’s departure opens up the possibility of talks between Aegis and Vincent Bolloré, who owns 29 per cent of the group. Mr Bolloré is also the chairman of Havas, a rival media buyer to Aegis, and has long been keen to find some form of cooperation between the groups.

That hope sent Aegis shares soaring 19 per cent, up by 9¼p to 59p, lifting them out of a trough where the shares had dipped to levels not seen since the mid1990s. Only two months ago the stock was trading at above £1.

However, for the moment Mr Bolloré intends to bide his time. The Frenchman has been unhappy with Aegis’s share price performance, and the stock is trading at half the price he bought in at, but has no active proposals for a tie-up. Aegis and Havas own the media-buying units Carat and MPG, which compete directly.

Mr Lerwill vigorously opposed any link-up with Havas, unless the French company was willing to make a full bid. Mr Bolloré tried several times to get two nominees placed on the board of Aegis, but this request was repeatedly voted down by shareholders at the request of management.

Alex DeGroote, a media analyst for Panmure Gordon, said: “There was no management premium for Lerwill. He certainly didn’t facilitate a deal with Havas. It may be that the new guy will.”

Mr Napier, who is also chairman of RSA, the insurer, will take over running the company on an interim basis, while a new chief executive is sought. Company insiders indicated that he had “no plans to initiate a strategic review” – City code for putting the company up for auction.

The interim leader has experience of marketing, having run AGB, the market-research group, in the 1980s. Apart from Carat, Aegis’s other business is Synovate, the market-research group, an operation that is supposed to be more resilient in a downturn.

The problems at Aegis stem largely from difficulties in Synovate, seen by Mr Lerwill as the growth driver for the group. Synovate’s United States business is heavily exposed to some of the weaker parts of the already faltering US economy, such as carmakers, and its performance is understood to have frustrated Mr Bolloré.

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