Eight days after two Prince George's County taxpayers launched a referendum drive designed to limit county government spending, County Executive Winfield M. Kelly has announced that he is instituting a freeze on all county hiring and any new capital expenditures.

Adopting the spirit of the dissident taxpayers' movement as his own, Kelly said yesterday that he would support the petition drive for a referendum on the charter amendment, since the drive was part of a "true, popular movement" for tax relief.

At a press conference yesterday, Kelly said he knew of the "tremendous demand for property tax relief" in the county and said he had "already produced a significant tax cut for the taxpayers" this year.

Kelly said he had been "concerned" about the effect of the referendum on his government "when we first saw it coming. We now find it compatible with our program of homeowners tax relief."

The referendum drive to amend the county charter is being pushed by maverick Democrats William Goodman and David Bird and has been named TRIM (Tax Reform Initiative by Marylanders). If approved by a majority of county voters in November the amendment would prevent the county from spending any more property tax revenue than it will receive in 1979.

Created after the tremendous success of Proposition 13, a property tax roll back measure passed by California voters earlier this month, the amendment was "a response to people who were really angry with the county executive and his bad management of government," said Goodman.

Goodman said the growing citizen support "is the reason Kelly decided to come aboard. I'm sure he saw it as a phenomenal threat to his campaign. After only one week, we have 2,600 signatures already."

Goodman's group must collect 10,000 valid voters' signatures by Aug. 21 to put the issue on the November ballot.

Kelly said he "could support the proposal . . . We have to reduce spending levels," he said. To do this, the present $443.5 million budget for fiscal 1979 would have to be cut by 3 percent, or $13 million.

Kelly said the county would also seek new revenues through "increased economic development" and through "expected increases in the state income tax revenues."

"There isn't any doubt in our minds we can provide the basic services for the next two years," Kelly said. "We don't plan drastic cuts - no libraries will close, no police stations. We will eliminate borrowing money (for new building projects), bike paths and things in recreation."

Kelly said he would also ask next year's General Assembly for a statewide rollback "to reduce the assessments for owner-occupied homes to as low as 35 percent. This could mean a 22 percent tax decrease for our homeowners."

Several council members reached yesterday said that "while they went along with the idea of tax reform" they were "concerned" with the possible effect on the county government if the amendment is approved.

Council member Samuel Bogley said, "We can't throw the (government) employes to the wolves and lock ourselves into a position of supporting this forever. Over 80 percent of our budget goes to salaries. Can we keep pace with the cost of living through this freeze?"

Kelly said he would support "the populist movement" only until he had "an opportunity to see how (it) worked. If we find services are greatly curtailed, we will go back to the people."

Goodman said Kelly made "a smart political decision" in endorsing the petition drive.

"He did it to defuse political dissent," said Goodman. "He saw it was extremely threatening to him. Just one week ago they were trying to punch holes in it. Now they are jumping in with us."