The Montgomery County Council agreed yesterday to consider rewriting a new county law controlling condominium conversions to correct what County Executive Charles W. Gilchrist said were "possible constitutional deficiencies" in the original version.

The council will hold an emergency public hearing Tuesday on whether to change the law. It will come on the day before the law faces a court challenge by area real estate interests.

The law is intended to give tenants or a group designated by the county government a chance to buy an apartment building before it is sold to an outside condo converter. By buying the building themselves, tenants can often purchase their individual units at a lower price than a converter might have charged.

The measure was passed last July along with a 120-day moratorium on condominium conversions when county officials became alarmed at the rapid rate at which rental apartments were converted to condominiums. Officials feared that the trend was displacing moderate- and low-income families and leaving them few rental alternatives.

The suit, filed in Circuit Court, also seeks to overturn the moratorium. If it is struck down, Assistant County Attorney Rocky Sorrell told the council, the tenant purchase law would be the only tool the county would have to slow the condo conversion process until a task force completes its study of the situation.

Gilchrist told the council in a memo that revising the measure is "imperative" in order to defend the law in court.

The county attorney's office said the existing measure is too broad because it delays sale of an apartment building even if the prospective owner doesn't intend to convert units to condominiums.

The office also objected that the measure sets no deadline for tenant associations to complete financial arrangement; for purchasing their buildings.

In addition to revising the law, the proposed measure would define tenant associations and is designed to prevent title problems that might arise under the existing law.