AdvancedAdvT Ltd (LSE:ADVT) said acceptances of its final offer for M&C Saatchi PLC (AIM:SAA) must be received by 1pm London time on 30 September.
The company, which is led by Vin Murria, best known as former boss of Advanced Computer Software Group, said M&C Saatchi shareholders "have a clear choice" now, with its final offer "providing higher value and greater deliverability within a shorter timetable" compared to the rival final offer from Next Fifteen Communications Group PLC (AIM:NFC).
Last month, Next Fifteen received regulatory approval in the UK and Australia for its proposed takeover of the advertising agency, while ADV said it had also received all mandatory regulatory clearances.
ADV said it had a series of "positive meetings" in July with the members of the M&C Saatchi executive committee and consequently "believes that the M&C Saatchi executive committee is committed to M&C Saatchi's future and looks forward to working with them".
Murria and the ADV board said they believe the proposal has "greater potential" than both Next15's offer and the current status quo "to deliver faster growth and significant value creation for M&C Saatchi shareholders and employees".
If the ADV offer for M&C Saatchi succeeds, it proposed moving from a standard London listing to trading on AIM and appointing a group non-executive directors including former Saatchi and Saatchi UK boss Tamara Ingram, ex WPP deputy finance director Christopher Sweetland, and Murria's former operations chief at Advanced Computer Software, Paul Gibson.
M&C Saatchi put out a statement in response to note the ADV's intention to accelerate the timetable, saying its directors continue to unanimously recommend that shareholders reject the ADV offer.
ADV said by accepting its offer M&C Saatchi shareholders "are not 'selling' their group" but instead will collectively retain majority ownership of between 53.7-59% of the enlarged group on a fully diluted basis, versus a current holding of 77.7%, which it said was over four times the percentage ownership offered under the Next15 final offer.
"The enlarged group will benefit from significantly broadening its access to additional institutional equity, which has the ability to accelerate a re-rating of the enlarged group for the existing shareholders, reflecting an improved market position, enhanced growth prospects, and increased liquidity of the shares. An increased rating will enable an acceleration of future investment and accretive M&A," it added.