It said its new Big King was the first time it had gone head to head with McDonald's and claims that in taste tests, six out of 10 people preferred their product.
The new burger, like the Big Mac, has two burgers, cheese, lettuce, onion, pickles and a toasted sesame-seed bun. However, the Big King weighs in at 4.4oz of beef, compared with the Big Mac's 3.2oz, is flame-grilled and is missing the middle layer of bread.
A spokeswoman for the company said that the Big King was different from other Burger King products because of the sauce, which has been specially developed to compete with that on the Big Mac.
But McDonald's said it was supremely unconcerned by the new launch and would not be selling a "McWhopper" in the near future.
"We think this a product that they have tried to launch in a number of different guises and it is nothing new," a spokeswoman said. "We have 77 per cent of the market in this country and we listen to our customers, so we have no need to pay any attention to our rivals.
"If we were number two then we would probably be trying everything we could to catch up, but as it is, we don't need to do that, so we don't need to worry."
Last year McDonald's, which trails behind Burger King in the US fast- food market, launched the Arch Deluxe to try to increase its market share, but it was not a success and was taken off the market shortly afterwards.Reuse content