The government was under fire yesterday over fears that Britain's iconic red postboxes could be axed if the Royal Mail national postal service is sold to a foreign firm.

The furore comes just weeks after London closed a loophole that could have seen Queen Elizabeth's head chopped off the kingdom's stamps if such a sale went through.

The Mail on Sunday newspaper said new owners would be free to redesign the pillar boxes, cover them with adverts, paint them a different colour and even remove the royal cypher.

The government has admitted that the draft legislation paving the way for Royal Mail to be privatised contained no special protection for the postboxes.

Nia Griffith, the opposition Labour Party's business spokesman, said: "The postboxes are much-cherished national icons but there is nothing to stop a new owner painting them yellow or plastering them with advertising. It's disgraceful."

However, Postal Services Minister Ed Davey insisted: "There is no evidence to suggest legislation is required on this."

A Royal Mail spokesman said: "We cherish our red postboxes. We are absolutely committed to ensuring they remain a part of communities throughout the UK."

The first of Britain's 115000 pillar boxes appeared just over 150 years ago, The Mail on Sunday reported.

Earlier this month the government moved to ensure that the sovereign's head would be kept on Britain's stamps.

They are the only ones in the world that do not carry the country's name - just the portrait of the monarch.

The current standard stamps, drawn up in 1967 by Alan Machin, are considered a design classic and a defining icon of Britain - as are the red pillar boxes.

In a bid to secure its future as Britons increasingly use e-mail, the cash-strapped government wants to sell off Royal Mail to give it an injection of private sector capital.

German and Dutch firms are reportedly among the front-runners to buy the service.