An audit of constituency party buildings, now being completed, has turned up around pounds 10m worth of lost buildings bequeathed in wills to the party and bought by local Labour groups before the war.
The National Executive Committee, led by Tony Blair, has ordered officials working from Labour's Millbank headquarters to raise millions of pounds by selling buildings that are too big, expensive to maintain or are losing money.
The move could help bail out the cash-strapped Labour Party which still has an estimated pounds 1.5m overdraft from general election expenses.
A survey of local Labour branches, sent out this summer, has turned up listed buildings and terraced houses given to the party by activists. The party has even discovered a garden centre owned by a London constituency group and a block of flats in the Midlands.
The property survey also included MPs' constituency offices, Labour clubs and buildings. It revealed that the party owns at least 400 properties worth more than pounds 30m. The party is now compiling a comprehensive list of what it owns. The day-to-day management, and the cost of maintaining the buildings, will remain with the local parties.
"We always had a good idea that there was a lot of property out there. There have been some surprises," said Peter Ballard, consultant property manager to the Labour Party.
"There are 50 to 60 buildings we didn't know about and some more we were vaguely aware of. They range from two-up-two-downs to massive Georgian houses in the centre of London and small blocks of flats. We have found buildings that date back to the 1790s. I was asked to investigate what we have and maximise the assets we own."
One of the newly discovered properties was a Victorian building near the gates of Windsor Castle which is being used by a local Labour club. Labour also found it owned a huge period house used by a local group in Forest Hill, south London.
The property team at Millbank consists of accountants, surveyors and solicitors who have been travelling around the country to advise local groups on how to manage their assets - and how to let unused rooms. But with the property market slowing, estate agents warn that the party may not be able to gain the top prices for unwanted buildings it could have gained earlier this year.
"So much depends upon the location of the building," said a spokesman for estate agent Knight Frank. "You have to consider whether the building is being utilised to its full potential. It makes sense to hive off some of it if it is surplus to requirements."
Many of Labour's grand period buildings, which are expensive to run, are being traded for smaller high street offices or purpose-built premises.
The party has advised local parties to merge MPs' offices in towns where they have several representatives.
In Edinburgh the party has just sold an imposing Edwardian residence owned by a local party for around pounds 350,000. The building, which has sweeping stairways and Doric columns, was too expensive for the local party to maintain. Millbank hired a team to refurbish the building before selling it to a business.
"The NEC are in charge of all of this," said a Labour Party spokesman. "There is a concerted attempt in the party to manage the property portfolio in an effective manner."