LONDON (REUTERS) - The British government has sold off a disused London underground station used as a secret wartime command centre, as part of its drive to repair battered public finances.

Britain's economy is growing again after three years of stagnation but national debt is at 75 per cent of gross domestic product, and the government says it wants to try to reduce that by cutting costs and disposing of unwanted assets.

The disused station, Brompton Road, closed in 1934 due to a lack of passengers, is one of many abandoned "ghost" stations that lie beneath the British capital.

Latterly used for training by air force cadets, it is in South Kensington, one of the most expensive parts of London, and contains old lift shafts which have been converted into rooms.

Tube trains still rumble underneath.

The Ministry of Defence, which owns the site, said it has already exchanged contracts with a buyer. The deal is expected to be completed within two months.

"As far as we're concerned the place has been sold and bought," a spokesman told Reuters, declining to name the buyer or the purchase price because of confidentiality agreements.

Estate agents said the area was popular with wealthy buyers from the Middle East and Eastern Europe and that the station, which was likely to have been sold for tens of millions of pounds, would be turned into luxury housing.

It has the potential for a helipad and a roof garden.

Local media said the station had been sold for 50 million pounds (S$82 million) to a Ukrainian billionaire.

The Ministry of Defence and the estate agent handling the deal declined to comment.

The British government says it has sold off more than 700 buildings or land plots since 2010, cutting the size of the government's property portfolio by at least 15 per cent and raising over a billion pounds.

The disused station was used as an air defence command centre during World War Two to protect central London from German bombers. Government officials say Winston Churchill, the then-prime minister, is thought to have spent time there.

The government is also selling off Britain's old War Office building close to the prime minister's office in central London.

Last year, it sold a lease on Admiralty Arch, an imposing archway which serves as a gateway from Trafalgar Square into the road leading up to Buckingham Palace, for 60 million pounds. It is now being converted into a luxury hotel.

The sale of a military barracks in Hyde Park is also being considered, a deal potentially worth hundreds of millions.