ConAgra Foods has given takeover target Ralcorp Holdings until Monday (19 September) to hold talks on its US$5.2bn bid or it will walk away from the table.

The US food maker said yesterday that it would withdraw its offer at 5pm ET on Monday if the two companies were not "in a constructive dialogue" on the bid.

Ralcorp rejected ConAgra's $94-a-share offer in August, the third bid it had turned down from the company in six months.

ConAgra claims Ralcorp has repeatedly turned down attempts to hold talks. Ralcorp is looking to split into two, with one business focusing on its private-label operations and one on its branded cereal arm Post Foods, and has insisted the move will provide greater value to shareholders.

There have been indications that some investors are unhappy with Ralcorp's stance. Yesterday, law firm Robbins Umeda, which represents shareholders in lawsuits, said it had started an investigation into "possible breaches of fiduciary duty" by the Ralcorp board for refusing to hold talks with ConAgra.

Robbins Umeda said that on 12 August, the day on which Ralcorp rejected ConAgra's latest offer, its share price was $79.02, compared to a bid worth $94 a share.

ConAgra said it had heard from "many" Ralcorp shareholders who are "urging" the company to hold talks on its latest "compelling, all-cash proposal".

The $5.18bn offer represented an "attractive multiple" of 9.4x Ralcorp's adjusted EBITDA, ConAgra said. It also argued that Ralcorp's spin off would lead to "value leakage" of $6 a share.

ConAgra added: "In contrast, ConAgra Foods' $94 per share proposal would provide Ralcorp's shareholders with compelling, certain value that reflects the strength of the combined businesses and the benefit of synergies ConAgra Foods expects to achieve."