WPP boss Sir Martin Sorrell has agreed a takeover

The Takeover Panel is investigating whether two parties were acting in concert to take control of the company.

It has declined to name the parties under suspicion.

But it has confirmed it is looking at the role of Nahed Ojjeh - the Paris-based widow of a Saudi billionaire - who recently surprised investors by amassing a 10% stake in Cordiant.

French advertising group Publicis - which last month abandoned its attempt to take over Cordiant - has admitted it has links with Mrs Ojjeh.

But the firm insisted it no longer had any designs on Cordiant - and denied being in a plot with Mrs Ojjeh to take control of the company.

Joint venture

Cordiant agreed last month to be purchased by its larger UK rival WPP, which already owns all of its debt.

But shareholders must approve the deal, and investment firm Active Value, which owns 30% of the company, could block it.

Some industry observers have suggested Active Value and Mrs Ojjeh were seeking to take control of Cordiant.

The plan - according to one theory - was to help Publicis buy at a cut-rate price Cordiant's stake in media agency Zenith Optimedia, a joint venture between the two companies.

Next move

But Publicis has denied any contact with Active Value or with Mrs Ojjeh.

"We are not involved in any plan. We formally deny any project," a Publicis spokeswoman told Reuters news agency.

But she did confirm that Mrs Ojjeh - daughter of the Syrian defence minister - owns about 1% of Publicis' shares.

Mrs Ojjeh also knows Publicis chairman Maurice Levy "and various other people in the group," the spokeswoman told FT.com.

The wealthy widow and chess patron's next move remains unknown, as does the motive and plans of Active Value.

If they blocked the WPP acquisition, Cordiant would probably be tipped into administration, and shareholders would get nothing.

Publicis had previously sought to acquire Cordiant on its own but was outbid by WPP and abandoned the effort in mid-June.

The Takeover Panel has said it is looking into whether Mrs Ojjeh properly disclosed her Cordiant stock purchases.