In response to widespread concern over the effects of development in Cambridge, the City Council last night initiated a plan that would require commercial developers to help pay for new affordable housing in the city.

After an extensive debate, the council voted to send a "home-rule" petition to the state legislature, asking that the city be allowed to charge developers a fee of three dollars per square foot on new construction that exceeds 30,000 square feet in area. The money raised by these so-called "linkage" fees would be placed in a trust fund to help build housing for city residents with low-to-moderate incomes.

Proponents of the linkage program said that although commercial development has enriched the city's tax base, it has exacted many other costs on the city, including traffic problems and a rise in the cost of living.

"There is a non-political' constituency in Cambridge who want to survive in this city," said Mayor Alfred E. Vellucci in support of the program.

But Councillor William H. Walsh said he was concerned that the development fees would threaten the city's economy. In recent years, the city has aggressively sought new development as a way to increase its sources of revenue.

However, Councillor Saundra M. Graham said she was concerned the linkage program might not be extensive enough to maintain low-income housing.

"I don't believe that people are really in support of affordable housing," said Graham. She said the fees should be higher than three dollars per square foot.

Under current law, all construction projects which require special permits pay a fee of of two dollars per square foot to the affordable housing fund.

A similar linkage program was put before the council in 1985, but the measure failed to receive the seven votes necessary for passage.

Vellucci attributed the measure's failure to objections from both Harvard and the Massachusetts Institute of Technology.

"I want to know how much money we lost as a result of that opposition," the mayor said.

Although City Manager Robert W. healy said he did not have such figures, council candidate Jonathan S. Myers said he estimated the loss at about $15 million.

Weapons Ban

Should the home-rule petition be adopted by the state, it would return to the council, which would then have the option of passing legislation to implement it.

In other business, the council:

--voted to expedite a report on the possibility of converting Harvard's affiliated housing into rent-controlled housing.

.asked City Solicitor Russell B. Higley to draw up a home-rule petition authorizing the city to ban semiautomatic weapons. A similar measure was recently adopted in Boston.

.asked Water Department Superintendant John J. Cusack. Jr. to appear before the council to discuss problems with the city's water supply.

.voted to support the initiative petition of the Massachusetts Municipal Association that would set aside 40 percent of the state's growth tax for aid to cities and towns.