The advertising giant WPP has said it will appeal against the decision by the UK's Takeover Panel which prevents it from wriggling out of a deal to buy media buyer Tempus.

WPP offered �434m, the equivalent of 555p a share, for Tempus in August, trumping a bid by France's Havas.

But WPP three weeks ago attempted to revise its offer, claiming there had been "material adverse change" in Tempus's prospects, particularly following the 11 September attacks, which caused widespread economic turmoil.

Earlier on Thursday the Takeover Panel, a self-regulatory body set up by the City to adjudicate on merger and acquisition disputes, denied WPP permission to withdraw its bid.

It now says it will hold a full meeting next week in order to hear WPP's appeal.

Revenue plunge

The panel's decision has added to WPP headaches including a meltdown in media spending, which the ad giant highlighted in a separate statement on Thursday.

Group revenues fell 6% in the July to September quarter, on a like-for-like basis, with takings at North American offices more than 11% down on the same period last year.

Takings at public relations and lobbying arms were worst hit, plunging 15% group-wide.

Economy blamed

WPP blamed the falls partly on the affects of the global economic slowdown, which have begun to spill over from the technology areas to "old economy" sectors.

And the turmoil stemming from the terrorist attacks on the US cost the firm at least $30m in lost takings in September alone, "without the opportunity to reduce operating costs".

"If the last three months of the year were impacted in the same way like-for-like revenues for the whole of 2001 could be down 2%," WPP added.

After dropping sharply at first, WPP's shares recovered to close up 6% at 590.5p,

Shares in Tempus also ended higher - up 4% at 530p.