The advertising giant WPP has been dealt a further blow in the long-running dispute over its takeover of media buyer Tempus.

WPP has lost its appeal against the decision by the UK's Takeover Panel which prevented it from wriggling out of a deal to buy Tempus.

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

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

The case is seen as a test as to how easy in practice it is to invoke the rarely-used adverse material change clause.

Advertising meltdown

Although WPP has lost its appeal, it had been told it can still attempt to overturn the decision through the Panel's Appeal Committee.

The Panel said it would on Monday or shortly after deliver to both parties detailed reasons for rejecting the appeal.

WPP said it would comment "in due course".

The advertising giant has been suffering from the meltdown in media spending.

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.

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".