The coalition government plans to sell up to 90 percent of the state-owned letter delivery business.Business Secretary Vince Cable said in September that a foreign company could acquire Royal Mail.

Although there was provision in legislation to protect the Royal family brand, there is nothing specific preventing whoever runs the Royal Mail in future from dropping the Royal head.

"I think it's very unlikely they would because, after all, it's a very powerful brand," he told BBC television. "We'll talk to the palace about whether any further changes need to be made."

The monarch's head has appeared on every British postage stamp since their invention in 1840, the Mail on Sunday newspaper said.