Consumer goods giant Unilever – the owner of Colman's Mustard – has rebuffed a proposed mega-merger with global food firm Kraft Heinz.

The company behind Heinz Tomato Ketchup and Philadelphia cheese said it had made a 'comprehensive proposal' about combining the two companies, but Unilever turned the offer down.

In an announcement, Kraft Heinz said: 'While Unilever has declined the proposal, we look forward to working to reach agreement on the terms of a transaction.

'There can be no certainty that any further formal proposal will be made to the board of Unilever or that an offer will be made at all or as to the terms of any transaction.'

Unilever, which also owns Dove, Ben & Jerry's ice cream and Domestos, saw its share price rocket 12% in London on news of the approach.

The Anglo-Dutch firm said the offer represented a premium of 18% of its closing share price on February 16, valuing the company at $143bn (£115bn).

Colman's is the oldest brand in the Unilever stable, and celebrated its 200th anniversary in 2014.

The mustard is still produced in the city, along with other condiments, at the Carrow Works site on Bracondale.