The Montgomery County Council and County Executive Charles W. Gilchrist are still at loggerheads over a controversial child-support payroll deduction bill passed last August. Gilchrist has said he will not implement the legislation, and repeated that position even after the council tried to alter the law last week.

The law, sponsored by Council President David L. Scull, would allow the county government to deduct child support payments from the paychecks of county workers, on the order of the clerk of the Circuit Court. The person receiving the payments would be able to request the payroll deductions even if the employe has not been delinquent.

Gilchrist has refused to implement the law, citing a county attorney's opinion that the law probably was unconstitutional. State law preempts the county from making such payroll deductions, according to that opinion, and the state makes payroll deductions only when a person has been delinquent in his or her child-support payments.

Also, under the council-passed county law, the court clerk, and not a judge, would be able to order the payroll deductions.

Scull thought he was solving the county attorney's problems with the legislation when he proposed some amendments at the last council meeting. But later, the word from the executive's office was "no deal."

The Montgomery council last week approved Gilchrist's request to hire a special, outside lawyer to represent the county in what is likely to be a protracted legal battle with Blake Construction Co., builders of the new executive office building.

The executive office building was completed for occupancy in 1981, one year behind schedule and up to $20 million over the original contract cost. Blake and the county have been trying to settle the difference ever since, with each side blaming the other for the long delay that led to the cost overruns.