Eighty per cent of the parking tickets issued against diplomats here go unpaid, D.C. Superior Court Chief Judge Harold H. Greene told the Senate District Appropriations Subcommittee yesterday.

Subcommittee Chairman Patrick J. Leahy (D-Vt.) urged that the city crack down on both diplomatic and congressional offenders of parking reulations. He suggested one way might be to require that license plates issued to diplomatic vehicles include the name of the country to which they belong.

"If not paying is done purely by tradition," Leohy said, "then given the financial condition of the city, it's a tradition that can change."

Th subcommittee released figures compiled by the city's Department of Transportation and Superior Court, which show tht in the period from Jan. 1, 1976, to March 31 of this year 37,905 parking tickets went unpaid by diplomats. The tickets represent more than $1 million in fines and penalties.

Five countries - the Soviet Union, Israel, Nigeria, Cameroom and Jeru - were responsible for more than 20,000 of the unpaid tickets. The Soviet Union, with 12,270 parking violations, led the list. Israel was second with 4,885 tickets, followed by Nigeria with 1,225, Peru with 1,084, and Cameroon with 880.

The figures issued yesterday confirm estimates previously made by The Washington Post and private citizen groups concerned with the issue of diplomatic immunity from parking regulations.

Embassies have long argued that their parking facilities are inadequate and that American diplomats abroad are granted the same privilege of ignoring parking restrictions.

The Soviet Union, the longtime leader in accumulating unpaid tickets, has an agreement with the State Department allowing embassy employees to park in the congested downtown area of 16th Stree NW between L Street and Scott Circle near their embassy. But police continue to ticket the cars parked there because the city is not a party to what the State Department calls an unwritten "mutual understanding."

Officials say this understanding allows American diplomats in Moscow to ignore parking restrictions near the United States Embassy. A similar agreement is said to exist between the United States and Isael.

The issue of diplomatic parking violations came up during the second day of hearings by the Senate subcommittee on the city's fiscal 1978 budget.

At yesterday's hearing, Douglas N. Schneider, director of the city's Department of Transportation, outlined previously announced plans to improve the enforcement of parking regulations by intensifying the booting of cars with outstanding parking tickets and other methods.

The figures released today indicate that if all the diplomatic parking tickets were paid, the city woudl receive $1,070,000. The figure reflects the fact that fines for parking tickets not paid within 15 days of being issued are automatically doubled.

The figures show four coutnries with no outstanding tickets - Grenada, Guinea-Bissau, Fiji and Laos.