Mayor Marion Barry's administration objected yesterday to allowing taxpayers already on the city's tax rolls to participate in a proposed one-time tax amnesty program that the City Council has indicated it will approve.

The city could lose millions of dollars if it forgives penalties and fines on delinquent taxpayers who already have been assessed and billed for the tax and who may be on a repayment schedule, Melvin W. Jones, director of the D.C. Department of Finance and Revenue, said at a hearing of the council's Finance and Revenue Committee.

Jones said in prepared remarks that the administration believes tax amnesty "sends the wrong message" to both honest taxpayers and tax evaders.

He added, however, that his department would be willing to help fashion an alternative to the amnesty program proposed by council member John Wilson (D-Ward 2), the committee chairman.

Under Wilson's proposal, residents who have not paid their taxes could come forward during a specified period and pay them, with interest, without civil or criminal penalties.

Wilson has estimated that the plan would bring in $20 million. However, the administration says it would bring in $8 million to $10 million.

Wilson said yesterday he would change his proposal to make the amnesty period fall after the regular tax season.

He also said he would modify the plan to withhold amnesty from those involved in criminal investigations or civil suits brought by the city, or those who already have payment agreements with the District.