Britain will start selling its remaining 30% stake in postal operator Royal Mail, which is worth about £1.5bn, as part of a drive to fix the budget deficit, finance minister George Osborne has said.

Mr Osborne also said government departments had found an extra £3bn in savings in the current financial year.

Mr Osborne is due to announce a new budget and fiscal targets on 8 July after his Conservative Party won a parliamentary majority in a national election in May. He said in March he was aiming to wipe out Britain's budget deficit by 2018/19.

Britain sold a 60% stake in Royal Mail in 2013, attracting criticism at the time from rival politicians and trade unions who said the firm had been sold off too cheaply after shares rose by as much as 87% following the sale.

Mr Osborne appeared to acknowledge those concerns as he made his announcement in parliament. "We will only sell our stake when we can be sure we are getting value for money," he said.

The shares were down 3% on the news.

No decision has yet been taken on whether the shares would be sold privately to investors or to the public, a Treasury official said.

The sale of further Royal Mail shares will begin this year, the finance ministry added.

It also said the extra savings found by government departments included a plan to sell land around London's Kings Cross station which was valued at around £345m.