The era of cheap food in Britain is over, the boss of Tesco has said.
Chief executive Philip Clarke said the growing pressure on global food supplies meant prices would have to go up.
"It's the basic law of supply and demand", he told The Observer.
Clarke also claimed customers were less interested in 'bogofs' (buy one get one free offers) than they used to be.
It comes as a poll suggested shoppers would be willing to pay more for food - as long it went to farmers, rather than into the pockets of supermarket bosses.
The survey, for the Prince's Countryside Fund, also found that 80% of consumers believed it was important to buy British produce.
Clarke's comments on food prices are significant not least because he represents the largest supermarket in the country.
He told The Observer: "Because of growing global demand, it is going to change.
"There's going to be more demand and more pressure.
"Over the long term I think food prices and peoples' proportion of income may well be going up but we'll be doing our bit.
"Unless more food is produced prices must go up. It's the basic law of supply and demand." It feels like a moment of confession."
Food writer Jay Rayner, who carried out the interview, wrote: "The boss of Tesco has finally said the unsayable."
On buy-one-get-one-free deals, Clarke added: "Customers don't like them as much they used to."
Shoppers prefer to get one cheap product than an extra one, he said.