Families in Alexandria and the District paid far more in state and local taxes at all income levels last year than elsewhere in the metropolitan area, while the tax burden in Arlington County, which also is densely developed, was among the area's lowest, according to new reports by the D.C. government.

The reports, which include income, real estate, sales and automobile taxes, also show that the tax burden in the District was relatively high compared with 50 other large cities around the country, but lagged behind the highest-tax cities, such as Newark; Bridgeport, Conn.; New York City, and Philadelphia.

Although the reports are not designed to provide exact year-by-year comparisons, the new study for 1986 shows that the tax burden on low-income D.C. residents has risen during the past five years compared with elsewhere in the area.

One other significant shift has been in the relative standing of Prince William County, which traditionally had been a low-tax area. Its tax burden last year was comparable to those in the area's three largest suburban counties -- Fairfax, Prince George's and Montgomery -- rather than being similar to those in low-tax, less urbanized Charles and Loudoun counties.

Philip M. Dearborn, vice president of the Greater Washington Research Center, said the low tax burden in Arlington probably stems from its relatively small number of school-aged children, the large amount of office and commercial development and "more conservative government."

Last year, Arlington had the lowest property tax rate in the area, when adjusted for average assessment levels, while Alexandria's property taxes were the area's second highest, after Prince William.

In the District, the effective tax rate on residential property was relatively modest, but income and sales tax rates were high.

Because of its unique status, the District government levies taxes that usually are imposed by both state and local governments. Thus, the comparisons provided in the reports show both the state and local taxes that residents of the different jurisdictions must pay.

The studies by the D.C. Department of Finance and Revenue are based on assumptions about the spending patterns and income tax returns of families of four, at five various income levels, ranging from $20,000 to $100,000 a year. The hypothetical families in the study all have two wage earners and own their own homes.

"Within the limits of what they do, they're pretty valid studies," Dearborn said, "but you have to be cautious about their assumptions and about making comparisons over time."

Dearborn noted that because of cuts in federal income taxes, which take effect this year, income tax rates and deductions have undergone major changes for 1987 in the District, Maryland and Virginia. He said the changes will lower the tax burden for both low- and high-income taxpayers, but may raise taxes for middle-income families.

Traditionally, taxation in the District had been the most progressive in the area, with low-income families paying a much lower proportion of income than those who are well-to-do.

However, because tax rates in the District had not changed for almost a decade, inflation pushed more relatively low-income families into higher tax brackets. The rapid increase in D.C. property assessments also raised tax bills even though rates did not change.

The relatively rapid increase in the tax burden in Prince William reflects the county's heavy population growth, bringing with it "more {government} services and problems," Dearborn said.

According to the new study, a family of four with an income of $35,000 a year paid $3,678 in state and local taxes in Alexandria and $3,565 in the District, but only $2,849 in Arlington.

The gap was much wider at higher income levels. For example, with a $100,000 income, a family paid $11,546 in D.C. taxes, but about $3,000 less in Arlington and about $2,000 less in Montgomery, Prince George's and Fairfax.