With an assist from Marion Barry, a panel of the D.C. City Council yesterday attacked Mayor Walter E. Washington's budget proposal to economize in the operation of the city's 36 advisory neighborhood commissions.

Barry (D-At Large), his party's apparent mayoral nominee, agreed with three other council members who said they will push for a full $1.1 million funding of the ANCs - as apparently required by law - instead of the $625,000 proposed by the outgoing mayor in his precariously balanced budget.

At the opening of the first of 14 council hearings into the proposed budget for the 1980 fiscal year, D.C. auditor Matthew S. Watson supported the position taken by the council members.

The larger amount is required by the congressionally enacted Home Rule Charter, Watson said. "While the council may increase this funding," he added, "no provision is made in the charter for reducing the funding."

For the past two years, however, Congress has cut the mayor's request for full funding - to $500,000 for fiscal 1978 and $625,000 for fiscal 1979, which begins next Sunday. The mayor embraced the 1979 congressional figure as his proposal for 1980.

"My interpretation of the charter," Barry said, "is that the District has no alternative but to apportion [the] full amount." He praised ANC members as "often the driving force" in their neighborhoods.

Voicing similar opinions were Willie J. Hardy (D-Ward 7), who chaired the hearing, and council members Polly Shackleton (D-Ward 3) and Hilda Mason (Statehood-At Large).

ANCs were created to advise city officials and other represent their areas on a wide range of municipal matters, including the monitoring of public services.

The money is used to maintain small staffs, maintain public information programs and sponsor small-scale public activities such as recreational events and clean-ups.

Watson also disclosed yesterday that D.C. budget director Comer S. Coppie has ordered the impoundment of any appropriated funds not paid by next Saturday from the city treasury to the ANCs. Watson said a "ballpark guess" of the amount is $60,000.

Carol Currie Gidley, a member of a Northwest ANC who serves on a citywide committee on ANC financing, denouned Coppie's order as "pure and simple Nixonian impoundment of funds - it's illegal."