Washington's flourishing consulting industry is the next target for the Carter administration's economy and efficiency drive.

Bert Lance, director of the Office of Management and Budget, disclosed in an interview that he is sending a "simple one-page letter" to the heads of all government agencies this week ordering them to report all their current consulting contracts.

"I think it's a real ripoff," Lance said of the multimillion-dollar government consulting business.

"I figure we've got more consultants running and doing nothing than we do lawyers."

The inventory of consulting contracts would be the first step in a drive to curb their use. It would probably be conducted in connection with the preparation for the fiscal 1979 budget, which begins in two months.

But even before that, a Senate Government Operations subcommittee is expected to focus on the same subject. Sen. Lee Metcalf's (D-Mont.) panel on reports, accounting and management queried government agencies last October on their use of consultants.

The first response - a computer printout of the energy agencies' consultants - is expected to be available Tuesday, according to staff member Gerald Sturges.

Sturges said that early last year the Civil Service Commission reported there were 10,700 government consultants, but the subcommittee staff has reason to believe there may be at least twice that many.

House and Senate Appropriations subcommittees also have studies pending on the use of consultants in specific agencies.

Those units have turned up evidence, one staff member said, of "revolving-door consultants," who work for an agency and then become consultants to the the same agency at greatly increased pay.

They have also found that several units of large departments like Health, Education and Welfare have contracted for similar studies without knowing of the overlapping work.

Lance said his interest in the issue was triggered by a letter from an Alabama lumber dealer complaining of the complexity of the form he was required to fill out by the Environmental Protection Agency. Checking revealed that the questionaire was being used by a consulting firm with an EPA contract.

"I think that's the cause of a lot ofh an EPA contract.

"I think that's the cause of a lot of our paperwork problems," Lance said.