The recipe, which includes tomatoes, malt and spirit vinegars, molasses, dates, Tamarind and spices, had remained unchanged for more than a century.

However a spokesman for Heinz, which bought HP Foods in 2006, told Channel 4 News that changes were made last November to the level of salt in the sauce.

“We have been gradually reducing the salt levels to come into line with Department of Health and health campaigners’ requirements,” he said. “We’ve done it with all our sauces – HP, Daddies. We had to meet the 2010 targets set by the Food Standards Agency.”

HP already has a reduced salt and sugar version, with 0.9g of salt in every 100g, and now the salt levels in HP Original have been cut from 2.1g in every 100g, to 1.3g.

Goaded by the celebrity chef Marco Pierre White – who has branded the new taste “disgusting” – fans have bombarded HP Sauce’s Facebook page, calling on Heinz to “bring back the salt”.

Forced to defend its move, HP Sauce commented on Facebook: “We believe that HP is still as great as always. We’re confident, as are the consumers that helped us with out taste testing… that this has not affected the taste of HP Sauce.”

The spokesman told Channel 4 News that minor adjustments were made to the spice levels in the recipe to compensate for the lack of salt.

‘Selling the family silver’

The iconic brown sauce was first concocted in 1899 by Frederick Garton, a grocer from Nottingham. Mr Garton sold the recipe for £150 to settle a debt with the founder of the Midlands Vinegar Company, Edwin Samson Moore, who launched it as HP Sauce in 1903.

We’ve done it with all our sauces – HP, Daddies. We had to meet the 2010 targets set by the Food Standards Agency. Spokesman for Heinz, owner of HP Sauce

Rumoured to be a favourite of politicians at the turn of last century, the sauce was named HP after the Houses of Parliament.

But despite its very British heritage, HP Foods – who also made Lea & Perrin’s Worcestershire sauce and Daddies – was bought out by US food giant Heinz for £470m in 2006.

The last British bottle of HP Sauce was produced in Birmingham in 2007, before the factory closed and production was moved to the Netherlands.

Workers at the site in Aston staged a mock funeral in protest at the closure, placing empty HP bottles in a coffin. Dressed as John Bull, protester Ray Egan (pictured above) said the move was akin to “selling of the family silver”.