The Environmental Protection Agency said yesterday it will file law-suits against more than 100 cities and 300 major industries that will not meet the nation's July 1 water cleanup deadline.

"We must not reward the recalcitrant," said Thomas Jorling, assistant administrator of the EPA, in announcing the enforcement action. "We are going after the big polluters."

Jorling said the agency will seek unprecedented fines of up to $10 million per company, based on the amount a firm saves by delaying installation of cleanup equipment, and penalties of $2 million or more cities.

The new policy represents a "drastic" acceleration of water pollution enforcement, according to Jeffrey G. Miller, head of the water enforcement division. However, the agency is not increasing the program's staff of 581 attorneys, inspectors and clerical helpers.

While EPA refused to name the companies and cities to be prosecuted, they will be chosen from a list of 600 companies and about 2,000 cities (all with populations over 10,000) that will fail to meet the deadline set by Congress five years ago.

The 1972 Water Pollution Control Act requires cities and towns to construct secondary sewage treatment plants and industry to install "best practicable" cleanup equipment - requirements that would eliminate about 85 per cent of the solids and organic matter in their discharges.

About 90 per cent of industry has met the deadline, but only half the cities have. Congress gave the cities $18 billion to build plants and promised them $45 billion move over the next 10 years in what has become the nation's largest public works program since the interstate highway system.

Of the 600 companies that are not expected to meet the cleanup deadline, 19 are in Virginia, seven in Maryland and none in the District. The roughly 2,000 noncomplying city sewage plants include one in the District, 43 in Maryland and 46 in Virginia.

EPA officials would not say whether suits are planned against Washington-area violators. Prosecution in all cases will depend on the health effects of the pollution and whether the city or industry has made a "good-faith effort to clean up.

The decision to prosecute 100 municipalities caught the National League of Cities by surprise. "EPA had assured us they had no intention of filing suits based on the July 1 deadline," said federal relations director Tom Tatum, adding that the House has passed a bill that would grant cities a five-year extension of the deadline.

"I think it would be irresponsible for EPA to prosecute us, because the federal government picked arbitrary deadlines without really knowing how long it would take to solve the problem," he said.

Municipal plant construction such as Blue Plains in the District, also was held up when the Nixon administration temporary impounded half of the $18 billion in aid.

Christopher Farrand, a Chamber of Commerce spokesman, Charged the Carter administration with "posturing a bit" by "coming down hard on laggard industries. By and large, industries have done a damn good job."

"The municipalities are much more laggard. The public should understand that their own local governments are a major part of the (water pollution) problem," he said.

Jorling said the agency will not only seek civil penalties but "also criminal sanctions where the discharger is operating with extreme recalcitrance."

Last year, EPA referred to the Justice Department for prosecution 150 industries and 20 cities that were violating water cleanup schedules. But 400 new cases over the next few months and a policy of seeking higher fines mean "this administration will be more aggressive" than the last, Jorling said.

In addition, EPA, which has been criticized for misallocation of sewage treatment funds, will review $1 billion worth of funds that cities have requested for collector sewers, pipes that run along most city streets, Jorling said.

"We believe that funding for some of this proposed sewer construction could be spent more effectively building ot upgrading waste treatment plants," he added.

Jorling also announced that the agency will conduct an "intense review" of the environmental effects of sewage construction projects - a controversial issue in Washington's suburbs. "We have to ensure that we are not funding facilities which stimulate rapid and unplanned growth and create a new level of environmental damages," he said.