Cattle on the farm, which is in the same area as three other recent cases, tested positive for the contagious disease that can affect all-cloven footed animals, the Department for Environment, Food and Rural Affairs (Defra) said.
Two other cases have also been confirmed since an initial outbreak in August, all of them in the southeastern county of Surrey.
"Positive test results for foot and mouth disease (FMD) have now been confirmed at the site where it was decided that cattle should be slaughtered on suspicion earlier this evening," a Defra spokeswoman said.
"The affected animals are within the existing protection zone and this now becomes the sixth infected premises since August 3 this year."
The spokeswoman said minor changes now had been made to the protection and surveillance zones.
The Press Association news agency said earlier that around 40 cattle were being slaughtered on the farm which is within the three-kilometre (1.8 miles) protection zone set up after the latest cases emerged near the town of Egham.
Some 1,800 animals have been slaughtered since the first outbreak, at what is usually one of the busiest times of the year for livestock sales.
The Press Association said tests were carried out after the animals showed clinical symptoms of the highly contagious viral disease.
The previous five cases have been the same strain of the disease.
Leaks from an animal disease and vaccine research laboratory were blamed for the initial outbreak in August, which was the first in Britain since 2001.
Government officials declared the country foot and mouth free on September 7 but the fresh cases near Egham led to the European Union re-imposing a ban on British meat exports.
England eased transport restrictions last weekend, allowing farmers to take livestock to slaughter for the first time since the last outbreaks.
Similar rules in Scotland and Wales had already been eased, while they were never imposed across the North Channel in Northern Ireland.
The 2007 outbreaks have raised the spectre of a repeat of a 2001 crisis, in which up to 10 million animals were culled and which cost the British economy about eight billion pounds (11.7 billion euros, 16.0 billion dollars).
Foot and mouth is a highly contagious viral disease that affects all cloven-footed animals, such as cattle, sheep, pigs, goats and deer.
It owes its name to the fact that the lesions it causes are found on the inside of the mouth and on the hooves of animals.
The disease is rarely passed to humans. The last reported human case of foot and mouth in Britain was in 1966.