Norman Ture, one of the few prominent supplysiders in the administration, announced his resignation from the Treasury Department yesterday. Ture's position of undersecretary for tax and economic affairs may not be filled, Treasury Secretary Donald T. Regan said yesterday.

The post of assistant secretary for economic affairs has not yet been filled after the departure from the administration of ardent supplysider Paul Craig Roberts on January 18. Ture and Roberts were the two most senior supplysiders working for the president.

Regan refused to say who would replace these economists at Treasury, or when someone would be named to either of their posts. "I am not prepared to announce a successor in the economic field," he told reporters. Ture said earlier that the search for Roberts' successor was being pursued vigorously.

The position which Ture filled was a new one created by this administration. It was seen as an indication of the importance of tax policy in the Reagan economic program. Regan said yesterday he had "made no decision about whether to fill that slot or not . . . this is a matter of structure at Treasury."

Both he and Ture stressed that the undersecretary was leaving his $59,500 a year post for financial reasons, and not because of policy disputes. However, Ture and other supplysiders have been increasingly isolated from policy-making according to administration sources.

The tax increases of the size included in the congressional budget resolution, and endorsed by Reagan, are "regrettable," Ture said yesterday. He has consistently argued for the supplyside view that lower marginal tax rates will stimulate savings and investment and growth. He has also argued that large deficits do not play a role in keeping interest rates high.

Ture and other supplysiders in Treasury pushed for a more optimistic forecast of the economy than that used for the president's budget in February, sources say. Regan himself embraced a gloomier view of the economy as the recession persisted.