The revelation follows allegations that one of Britain's most powerful crime families gave pounds 2,000 to Labour, possibly to the Islington constituency, before the last election.
The Neill committee on standards in public life, which will publish its report next month, will recommend limits above which donations must be declared, and which are almost certain to be legally enforced by the Government. They may well be lower than the pounds 5,000 limit already set by the parties.
Although all three parties have promised to disclose national donations over pounds 5,000, local payments do not have to be disclosed.
Labour, which has published national figures for two years, told the committee the loophole should be closed. It provides a means by which donors who do not want to be named can keep their identities secret.
A spokesman for the Neill committee said it did not intend to see it recommendations "blown out of the water" by letting the loophole continue.
Labour says the sums given to the national party by constituencies are "negligible" but cannot give an exact amount. The figure is included with "membership donations" of pounds 515,000 in its 1997 report.
The Tories received pounds 750,000 in donations from constituency parties last year, but do not name donors to local branches.
Labour has moved to rebut allegations that Tommy Adams, a London gangster jailed last week, gave money to the party. It said no such donation had been made nationally, but it could not rule out a local payment because officials had been unable to contact former treasurers.Reuse content