The document gives Tempus shareholders until 3pm on October 1 2001 to respond to WPP's offer.
The issue of the offer document is expected to excite a response from Havas Advertising, which has been sitting quietly on the sidelines for the last month since WPP made its 555p-a-share counter-bid topping Havas's original 541p-a-share offer.
Analysts are expecting Havas to come back with a higher offer for Tempus, possibly as high as 575p.
Last week, the French group extended its 541p offer for Tempus Group until September 17. This followed the announcement that it now controls or has received irrevocable undertakings for 29.3% of Tempus.
It has been widely predicted that if Havas comes back with a higher offer, WPP will walk away. As WPP already owns 22% of CIA-owning Tempus, it would do so with a healthy profit.
WPP CEO Sir Martin Sorrell built up his holding in the company for an average price of 220p a share, giving his group a healthy profit.
However, a point which could hamper a higher Havas bid is its falling share price. The Havas bid comprised a combination of cash and shares, and its share price has fallen sharply since it first made its bid in July.
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