Prince George's County Executive Winfield M. Kelly Jr., who has attempted during this election year to present himself as a leader of the property tax rebellion, yesterday said he plans to cut the county's property tax rate by 15 cents next year and hold the county budget to a 4 percent increase.

Kelly said both actions are necessary if the county is to adjust to a tax ceiling referendum on the November ballot that he supports and expects to pass. The referendum would freeze the county's total property tax levy at $140 million - the amount raised for the fiscal year 1979 budget.

"I believe it's what the people want done," said Kelly, who is faced with a tough re-election fight against Republican Lawrence J. Hogan. "And I don't expect it to result in a cut in services."

The county executive said early estimates from state tax assessors indicate that Prince George's property tax assessments will increase an average of about 7 percent this year. A tax rate cut of 15 cents will be required, he said, to keep the total property tax revenues at the $140 million figure.

Local property tax reliefs currently supply the country government with 35 percent of its revenue. The 4 percent increase in next year's budget. Kelly said, would come from state and federal sources that supply the other 65 percent.

Kelly noted that a 4 percent budget increase would be the lowest in this decade. During his four years in office, the budgets have increased an average of 6.5 percent each year. From 1970 to 1974, when Republican William Gullett was the county executive, the budgets increased yearly by an average of 12 percent.

Hogan, the former congressman from Prince George's dismissed Kelly's tax pronouncements as a "shell game" and said that if he is elected county executive he will cut the budget.

"I'm not surprised that Kelly says he's going to cut taxes in an election year." said Hogan. "But the fact is that he can cut it a lot more than he will. The 1979 budget shows a $20 million surplus that Kelly stored up just for this election. A $10 million surplus is judicious; $20 million is excessive. The first thing I'd do as county executive is give that $10 million back to the taxpayers."

Hogan said he could cut the $450 million county budget "by eliminating all the duplication that now exists. Right now, you've got various deparments with their own printing, data processing, purchasing and design and construction departments. They all could be easily centralized."

Kelly said the $20 million surplus listed in the current budget resulted from savings from the previous year. "Every year, we have a goal for the bureaucrats to save as much of the money appropriated for their departments as possible," said Kelly aide John Lally. "People who do that rise within the administration - they are looked upon with favor."

While Hogan charged that the $20 million surplus" is just sitting there "doing nothing," Lally argued that the money is being applied toward next year's budget. "Hogan must think we're absolute idiots if he believes we're not using it for tax cuts," said Lally. "That surplus money is the reason we could cut the tax bills this year."

The one thing that Kelly and Hogan agree on is their support on the tax referendum known as TRIM (Tax Reform Initiative by Marylanders), a referendum initiated by two insurgent Democrats in the county, which has been embraced by most of the county's political establishment.

At his Upper Marlboro press conference yesterday, Kelly said he will implement the objectives of the TRIM referendum even if it is defeated on the November ballot.

Hogan said in an interview that "the county can live well within TRIM - I favor it and have all along."

Although the Prince George's Trim has been compared to California's Proposition 13 and a measure by the same name in neighboring Montgomery County, its objective is somewhat different. The other measures drastically reduced property tax assessments; Prince George's TRIM merely freezes the total property tax levy.

In fact, the two insurgent Democrats who created TRIM - William Goodman and David Bird - were attempting to use it as a means of reforming the state tax system to effect a greater reliance on the income tax, which they believe is the more progressive tax.

"We were certainly not interested in cutting back on necessary social services," said Bird, who is now a Democratic candidate for state delegate in the New Carrollton area. "What Kelly is now doing leaves me a little miffed. I think he may be acting prematurely."

Kelly said he hopes the 4 percent cap on the budget increase will not force the county to cut services. "When there are cuts," he said, "the social services are the first to fall by the wayside. I'm going to make a special effort to see that that doesn't occur."