If any bid from Mr Boparan is made, it may end Northern's plans to merge with Irish firm Greencore.

BBC: Northern Foods shares up on approach by Ranjit Boparan

The Unite union says Greencore is abolishing premium rate overtime and bank holiday working payments and threatening staff with redundancy.

BBC: Greencore workers petition bosses in Dublin over pay

In a statement, Greencore said the sauce contained meat supplied by the ABP Food Group's Nenagh plant in County Tipperary, Ireland.

BBC: Three held in horsemeat mislabelling investigation

Unite union said Greencore bosses did not restore overtime and enhanced holiday pay after staff agreed to suspend them to help the firm.

BBC: Greencore workers win compensation over stopped pay

Greencore said its priority was the "long-term sustainability" of its site.

BBC: Greencore workers win compensation over stopped pay

Northern Foods and Greencore plan to create a new firm called Essenta, with both sets of shareholders due to vote on the proposed deal on 31 January.

BBC: Northern Foods shares up on approach by Ranjit Boparan

Greencore, which supplies convenience foods to supermarkets, said it "acknowledges the recent decision in the tribunal case" but the dispute with the union over pay rates was ongoing.

BBC: Greencore workers win compensation over stopped pay

Last November workers won an employment tribunal over the pay cuts but the union said Greencore had since failed to restore the temporary changes and issued new contracts.

BBC: Hull Greencore cake staff strike over pay

The petition was handed to Greencore's company secretary Conor O'Leary.

BBC: Greencore workers petition bosses in Dublin over pay

Greencore is the UK's biggest sandwich maker.

BBC: Northern Foods shares up on approach by Ranjit Boparan