Tempus has urged the City's mergers and acquisitions watchdog not to allow WPP to wriggle out of its £432m bid for the media buyer.
The group argued that there were no reasons why the 555p-a-share deal should not go ahead based on the substance of a submission made last week by WPP to the Takeover Panel.
WPP, which is anxious not to overpay for Tempus in light of the steep advertising slowdown, had asked the panel to invoke a get-out clause following what it believes has been "a material adverse change in the prospects of Tempus".
Tempus, which has seen the points raised by WPP, said: "The board is firmly of the view that there are no grounds for allowing the material adverse change condition to be invoked."
Tempus submitted its case to the panel late on Tuesday. Both companies have declined to comment on the details of their arguments, but both claim to be equally sure of their cases. A decision is not expected until next week at the earliest.
Industry sources doubt that the panel will let Sir Martin Sorrell, WPP's chairman, off the hook for fear of establishing an unwieldy precedent. Sir Martin's likely stumbling block is that the material adverse change clause refers to individual businesses rather than entire sectors and Tempus has avoided issuing a profit warning.
WPP and Tempus shares both gained 10p yesterday to 538p and 507.5p respectively.Reuse content