President Carter has ordered his Cabinet members and staff to cut off any speculation about a tax cut this year, saying such talk tends to undermine the anti-inflation campaign.

In a memo sent out Aug. 2, Carter sought to end the recurrent discussion that he might propose an antirecession tax cut this fall to take effect in 1980.

In his memo, Carter said, "Economic conditions do not require a change in budgetary policy this year, including any tax reduction program, and I do not contemplate proposing any such change."

Informed officials said Carter has gone beyond that memo language and has said he would veto any tax-cut bill sent him by Congress this fall.

The president has not called for a tax cut either this year or for 1980, and there seems to be little chance that Congress would enact one this session. Carter has said he will stock with his current economic course.

However, the president has raised the possibility that he may propose a tax reduction in January if the recession proves to be deeper than expected, probably including a cut in Social Security taxes and incentives for business.

Carter reiterated in his memo that he will continue to monitor the course of the economy before coming to any decision on the issue. Key congressional leaders support his position.

Carter's memo indicated concern at the White House that conflicting impressions of the president's policy might feed the growing political pressures for an anti-recession tax cut.

Congressional Republications have proposed an immediate across-the-board reduction in income tax rates and are expected to press their proposal during consideration next month of the second budget resolution for fiscal 1980.

Carter's comments to a group of congressional Democrats three weeks ago created some confusion, with some of those attending the private session believing the president had opened the door to making a tax-cut proposal of his own in October.

Later, the White House said Carter's remarks had been misinterpreted.

In the memo, Carter said he remained "committed to a policy of fiscal and monetary restraint" and said any speculation to the contrary from administration officials was undesirable.

He ordered the officials to clear any suggestions for deviation from his policy with James T. McIntyre Jr., director of the Office of Management and Budget. CAPTION: Picture, President Carter, listening to Esteban Torres, is accompanied by another senior staffer, Sarah Weddington. AP