The head of Tesco has pledged to bring meat production "closer to home" and work more closely with British farmers in response to the horsemeat scandal.
Philip Clarke said Tesco had also introduced a new testing process and that from July all chicken sold in its UK stores would be from British farms.
Mr Clarke and Environment Secretary Owen Paterson are to address the National Farmer Union's conference.
A NFU poll found 78% of people want more British food in supermarkets.
Speaking to the BBC, Mr Clarke said he could not guarantee "right now today" that all of Tesco's products contained exactly what was on the label, but "that is our objective", he added.
"I'm sure that we will be able to say that in the future, once the testing regime is completely in place."
He said on the 300 tests that they had completed " most of them are fine" but that "three is too many".
Farmers' anger at the horsemeat scandal will be reflected at the national conference, NFU leaders have said - which is being held in Birmingham.
Many farmers believe the crisis over mis-labelled food has damaged consumer confidence in the supply chain.
NFU president Peter Kendall said: "Farmers have been furious about what has happened."
Gate to plate
"Farmers have spent many years working to ensure the British supply chain is fully traceable from farm to pack, and have upheld strong principles which are embodied in assurance schemes like Red Tractor.
"For me this is fundamental for consumer confidence."
But there is also a growing sense that this may be a moment of opportunity for British farmers.
They believe that tight regulations, including those introduced in response to the BSE crisis, mean their part of the food industry now sets the standard for others to follow.
Farmers have long called for the food supply chain, which can involve many traders and processors between farm gate and consumer plate, to be overhauled and simplified.
BBC rural affairs correspondent Jeremy Cooke said they hoped the horsemeat scandal could mean the rest of the industry - and the government - was ready to listen.
Meanwhile, a poll for the NFU suggested that more than three-quarters of people wanted supermarkets to stock more food from British farms.
Also, some 43% of the 1,000 people surveyed said they were more likely to buy food traceable from UK farms in the wake of the horsemeat scandal.
Mr Kendall said: "Our research also demonstrates the strong demand for British-farmed products, and so retailers, processors and food service companies have a responsibility to ensure there is clear country of origin labelling on the products that consumers purchase."
Mr Clarke said his supermarket would work more closely with British farmers in response to the horsemeat scandal.
"The testing regime is intended to ensure that if it is not on the label it is not in the packet, if it is beef, it is beef, and nothing else.
"And that is the most comprehensive testing regime I have ever seen, and it's happening right now.
"The second thing is we're going to bring meat production a bit closer to home. We do buy some, particularly for our frozen products, out of Europe, and as we can we'll bring it closer to home.
"And the third thing is we're going to have more partnerships, more collaboration with farmers."
He added: "I hope that it doesn't mean price increases, but I can't stand here today and tell you that it won't.
"I hope it doesn't, I'll work to make sure it doesn't."
Chief executive of Sainsbury's, Justin King, said Tesco's announcement "highlighted how important a detailed knowledge of and involvement in your supply chain is".
He said his supermarket was committed to doubling the amount of British food it sold by 2020.
The director of the International Meat Trade Association, Liz Murphy, said passing off horsemeat as beef was criminal behaviour that had to be stamped out, as imported meat should be of equal standard to that produced in the UK.
"The public health and animal health conditions have to be the same," she said.
"So when we supply meat from outside the EU, that has to comply with the same conditions that our farmers do and our manufacturers and factories do in the UK."