The offer was made to the French bank BNP which yesterday rejected Warburg's initial offer to buy out its 84 per cent stake. The offer values the company at FF4.88bn (pounds 630m). BNP failed to make any contact with Warburg by yesterday's noon deadline, but issued a statement saying it "is not and never has been disposed" to sell its CIP shares.
BNP made a lower offer to the minority shareholders last week, worth FF186 per share.
It is thought Warburg's extension of the offer may allow time for other minority shareholders to start complaining about the level of BNP's offer.
Warburg insists that its offer is serious and that it would happily take control of the company. If successful it would have several options which would include continuing to trade CIP as a single entity or breaking it up. CIP takes small stakes in quoted companies.
Warburg has a 3 per cent stake. According to records filed nine months ago other minority shareholders include Scottish Value Trust, Paribas and a collection of French institutions.
The battle for control has brought with it a clash of different banking cultures, pitting the comparative sleepy Paris bourse against the aggressive tactics of a City of London arbitrage department.