The Tories say that currently meat labelling is "misleading"
Only meat "born and bred" in Britain should carry "British" labels, the Conservatives have said.
Under current rules, meat from animals farmed in other countries processed in the UK can be packaged as British.
The Tories say this is "misleading", and have enlisted the support of celebrity chefs and charities.
Shadow environment secretary Nick Herbert told the National Farmers Union (NFU) there was a need to bring in more "honest" food labelling.
The Conservatives want to introduce a bill demanding compulsory country-of-origin details on packaging, which would require products carrying the UK flag to be born, reared and processed in Britain.
Mr Herbert said: "For a decade Defra (the Department for Environment, Food and Rural Affairs) has promised to clamp down on misleading information, and leading supermarkets gave a commitment in a voluntary code that they would not sell imported meat processed in the UK under a British label. Yet poor labelling persists.
"People have a right to know where their food comes from. Meat labelled British should be born and bred in Britain, raised to our high welfare standards."
He denied it was a campaign to put British producers first.
"Clear labelling will empower consumers, not restrict their options.
"Other EU countries fight for the interests of their consumers and their farming industry within the trading rules. It's time for the British government to show the same spine."
The campaign is supported by a number of bodies including the NFU and the RSPCA, and comes after an ICM poll commissioned by the Tories found 87% of people supported country of origin labelling.
TV chef Hugh Fearnley-Whittingstall said the labelling would help protect consumers.
He said: "Consumers have a right to know where their food comes from and what's in it.
"Any policy, whether it's pursued by our government or our retailers, that stands in the way of that is wrong and must be fought."