Attorney General Francis B. Burch told Gov. Marvin Mandel today that few of the proposals now before the General Assembly to alter the Maryland property tax assessment system can be considered constitutional.

In a 13-page opinion prepared at the governor's request, Burch severly limited the way that the Assembly or the executive can tinker with the system and provide the relief promised to Maryland homeowners, who have protested loudly over their rapidly rising property assessments used to calculate taxes.

Burch ruled that any proposal to freeze assessments at their current level, to limit the amount assessments can be increased, or to grant exemptions to assessments by fixed amount would "present both equitable and constitutional problems."

Burch ruled, however, that proposal to increase the inflation allowance for all property assessments or only for residential property would be held constitutional. Currently homes are assessed at fair market value less 50 per cent as an inflation allowance. There are several bills before the Assembly that would raise the inflation allowance to 60 per cent.

Since Maryland counties depend on the property tax for most of their income. Burch warned against passing a law that would later be struck down in court and cause the counties "considerable loss in revenue."

"I'm glad. This should help our effort in discussing the issue of tax reform in Maryland," said Prince George's County Executive Winfield M. Kelly Jr., who has asked that the Assembly allow him to levy a "tier tax" that would divide property into three categories with separate tax rates.

Last week Mandel's chief legislative aide, Alan M. Wilner had to postpone a presentation of the governor's own proposed legislation, apparently to ensure that the bill met Burch's specifications.

Legislators say the property tax assessment issue is easily one of the most important issues facing the Assembly this session. The issue, they say, has upset their constituents, who have blamed the state, not the counties, for the high taxes.

Burch made a recommendation, in the form of a "variation," that would pass the burden of high assessments and taxes back to the counties. His proposal would require that the inflation allowance for each subdivision be increased by the average increase in residential property value in that subdivision during the previous year.

Although Burch showed sympathy for the homeowners, saying that "the increased tax burden has had a considerable impact on homeowners who own property simply for residential rather than for investment purposes," he also urged that "any steps taken in that direction (tax relief) be taken with circumspection."

In the last three years inflation has pushed property values up 50 per cent in Maryland while a new statewide assessment method has been so successful that assessments have uniformly kept pace with that inflation. Citizens have complained that it allowed jurisdictions to raise new revenue with a higher tax base without raising tax rates.