The accuracy of property tax assessments in Montgomery County, which have risen twice as fast as the inflation rate and aroused a wave of citizen protest, "could be substantially improved" by more computerization and professionalism in the assessor's office, a citizen task force has concluded.

"We did find that there were inequities (in property assessments), most of which results from procedures used by the state Department of Assessment . . . (which is responsible for assessing property in all Maryland jurisdictions). We think the least the state could do is make sure that they are up to the latest state of the art," said Scott Fosler, chairman of the Task Force on Real Property Assessment Practices.

In its final report to the County Council, the year-old 20-member task force recommended that the Montgomery assessor use a computer-based system, such as the one used in Fairfax County, to improved the accuracy of assessments and make them easier for citizens to understand.

It recommended that the county itself install a computer system if the state Department of Assessment will not fund it. It said that such a system is "well within the range of reasonable cost."

The task force did its own computer study of the accuracy of property assessments in Montgomery County, finding inequities on several levels.

Overall, it found about 43 percent of the residential properties sold in its study year to be in a middle range, assessed at between 38 to 44 percent of sale price. But 18 percent were significantly underassessed and 39 percent were significantly overassessed in relation to the entire study group.

A comparison of redidential properties in different areas of the county produced even wider disparities.For example, in Poolesville only 9 percent of the properties sold in the study year were underassessed, compared to 60 percent in Barnesville. And in Gaithersburg, 58 percent were overassessed, compared to 18 percent in Clarksburg.

The task force also found higher-priced property more likely to be underassessed than lower-priced property. And while the study indicated that commercial and industrial property may be underassessed relative to residential property, task force members split sharply on that question.

In its report, the task force said the assessment system in Montgomery County "probably compares favorably" with other countries in Maryland and nationwide. But it had harsh words for Willaim Shoemaker, the state director of assessments, who it said failed to provide support "for performance standards . . . above the mediocre statewide level."

Shoemaker took issue with the task force's characterization of the statewide standards as "mediocre," saying Maryland's assessment system would compare favorably with that of any other state.

The level of scrutiny that Montgomery County taxpayers are giving their property assessments has been steadily rising, the task force emphasized.

Between 1972 and 1977, for example, assessments on residential property increased by 102 percent while the Consumer Price Index rose 48.9 percent. Because there has been no offsetting decrease in the property tax rate, the task force said, property taxes have increased with assessments.

Consequently, the task force reported, citizens have focused on the assessor as "a visible and convenient target for general complaints about taxes, inflation and the cost of government." Citizens have become unwilling "to accept margins of error or assessor judgement that have been accepted in the past."

Besides the computer system, the task force recommended these changes in assessment standards and procedures:

Using the "income capitalization" method to help determine assessments for commercial and industrial properties. This method, now used for apartments, is expected to produce higher assessments of large commercial properties such as shopping centers.

Documenting assessments by showing the statistical techniques used, the range of possible appraisals for each piece of property and the judgements used by the assessor in arriving at a final figure.

Training assessors more extensively, and hiring assessors with special training to assess commercial and industrial property.

Giving the county a more direct influence on the assessment system by having the county government annually analyze and evaluate the assessmeny system. Also, the task force recommended that the county fund a pay differential so that employes of the state assessment office in Montgomery County are paid locally competitive salaries.

Changing the appeals process so that property owners have a better chance. The task force concluded that the current system corrects "only the most blatant relative inequities" and recommended holding the assessor on appeal to the figures he originally used as one means of combatting the property owner's handicap.

In general, the task force stressed that its recommendations are designed only to solve inequities in property assessment. Relief from the property tax burden will come only from "restraining the cost of government." And it said relief for those on low or fixed incomes should come through an extension of the property tax circuit breaker, now before the legislature.

The task force's 29-page final report has been given to the County Council, and Council President Elizabeth L. Scull said Council members will consider the report and its recommendations in the coming weeks.