A Royal Mail postal van is parked outside homes in Maybury near Woking in southern England on March 25, 2014. Reuters/Luke MacGregor

Britain has raised 750 million pounds ($1.16 billion) by selling half of its 30 percent stake in Royal Mail, it said on Thursday, adding it saw no reason to keep any holding in the postal service that was wholly state owned until 2013.

The sale of the first batch of shares in the 500-year-old postal operator two years ago attracted criticism from opposition politicians and trade unions who said the firm was sold off too cheaply after the shares jumped as much as 87 percent.

Having sold in 2013 at 330 pence in one of Britain's biggest privatizations for decades, the government offloaded its latest 15 percent stake late on Wednesday at 500 pence.

The stake sale led the shares to open 3.8 percent lower, at 497 pence on Thursday morning.

Business Secretary Sajid Javid said the sale represented good value for taxpayers.

"Royal Mail has demonstrated that it can thrive in the private sector," he said. "It now has the ability to access the funds it needs to ensure that it has a sustainable future and can adapt to the changes in the postal market.

"The Government sees no policy reason to keep its remaining stake in Royal Mail."

In a speech on Wednesday, Chancellor George Osborne said the government would also award up to 1 percent more of Royal Mail's shares to staff, after giving them 10 percent in 2013.