The Environmental Defense Fund has complained to President Carter that one aspect of the administration's anti-inflation effort could cripple several new programs administered by the Environmental Protection Agency.

In a letter to Carter last week, Arlie Schardt, executive director of the lobbying group, said that the administration's plan to freeze existing vacancies in the federal workforce could have as many as 1,200 budgeted jobs in EPA unfilled.

"We fully suport your efforts to curb inflation, but do not believe that the achievement of this goal requires the guting of environmental and other health and safety programs." Schardt said.

In his anti-inflation speech to the nation last week the president announced that he was immediately ordering that federal agencies fill only one of every two vancancies as they occur. He said this would reduce the federal workforce by about 20,000 jobs, further cutting the budget deficit.

It was not clear at the time what would be done about vacancies that already exist in the government. But yesterday Bob Dietsch, a spokesman for the Office of Management and Budget, confirmed that these vacancies - which numbered 20,000 jobs at the end of August and probably fewer at the time of the President's announcement - have been frozen.

This freeze on existing vacancies will hit hardest those agencies that were expanding most rapidly with new programs and duties. EPA, to the joy of environmentalists, was one of the few federal agencies allowed to grow under the budget Carter proposed a year ago and Congress approved. The expansion was mainly aimed at strengthening enforcement of laws previously passed.

Dietsch said there are exceptions to the freeze, chiefly for jobs involving "the safety of human life and the protection of property."

Schardt and other officials of the Environmental Defense Fund said their principal concern was the likely impact the freeze will have on new EPA programs for which job slots had been authorized but not filled at the time of Carter's announcement.

Schardt said he understands the freeze could prevent the hiring of more than 100 staff aides newly authorized for EPA's safe-drinking water program and effluent guidelines division, 120 jobs authorized for the implementation of the 1977 Clean Air Act Amendments, and 200 aides to be hired to implement the new Toxic Substances Control Act.

Other defense fund officials said they had been told an exemption from the feeze is likely to be granted for the toxic substances program but not for other EPA ventures.

Bob Rauch of the defense fund's Washington office argued that the freeze could backfire by feeding inflation.

"If the personnel are not there, there will be delays in processing all these applications and that could be inflationary itself," he said.

Rauch said the environmentalists could support letting half the new vacancies go unfilled, but not the freeze on existing vacancies.

In other developments at the White House yesterday, officials abruptly canceled a nationally televised news conference by the president scheduled for today. Reasons cited by presidential aides included the closeness of the Nov. 7 congressional elections and the delicate situation in the Middle East peace negotiations. Carter does not plan another news conference until after the elections, officials said.

The White House also announced that the president will stop in Duluth, Minn., Friday to campaign for Democratic candidates en route to Washington from earlier campaign appearances that day in Portland, Ore., and Sacramento, Calif.

In addition, officials said Carter will travel to Kansas City Nov. 9 to address a farm group.