Ronald Reagan, promising a broad new attack on the "missing issues" of the 1980 presidential campaign, today accused President Carter of "Jimmying" government economic figures as a pre-election ploy.

Reagan charged that the Carter administration had "changed the ground rules" in determining last week's producer price index figures for September, causing the inflation gauge to decline rather than rise.

"The creative use of statistics by this administration is going to prove to be a cruel hoax," Reagan said.

In Washington, Charles Schultze, chairman of the Council of Economic Advisers, called Reagan's charge "absolutely false, irresponsible and based on a zero acquaintance with the relevant facts."

The September producers price index -- one of the government calculations designed to measure the inflationary rate -- declined by 0.2 percent.

But Reagan charged that the administration "stuck in something that never before had been in there to make it go down." Reagan did not identify the added ingredient but aides later said he was referring to auto industry rebates, an item that has not been used in the calculations before.

Reagan later said the index would have risen 0.4 percent if the administration had left the price index formula the same in September.

"The decision to move to transaction prices for autos was made a year ago by Bureau of Labor Statistics commissioner [Janet] Norwood and her staff with no communication with people outside the bureau," Schultze said in Washington. "The charge is part of a continuing revision and improvement of the producer price index. The elements of the revision were described in a published article in the December 1979 Monthly Labor Review, although the auto change itself was not specifically mentioned.

"This is a very serious charge. Gov. Reagan ought to document his allegations [or] apologize to the hard-working professional men and women who work year in and year out under administrations of both parties to produce and improve the statistical system of the United States."

Reagan's sharp attack came at a shopping rally in the pivotal state of New Jersey as he opened a week of campaigning in target states in which the outcome of the election could swing.

In a strong attack on both Carter's economic policy and the way it is presented to the public, Reagan said the administration has "taken to making highly questionable uses of official government statistics to sugarcoat the bitter economic news." Reagan contended that inflation is worsening, despite the indications from the producer price index. He predicted that the worsening would show later, perhaps not until after the election, and that at that time the Carter administration would drop auto rebates from the calculations once again.

"Measured by the way this administration has used the 'imperial presidency' over the past year," Reagan charged, "I am not surprised by the recent -- if you'll forgive me -- 'Jimmying' of official government statistics."

Reagan said the administration changes in the formula for the index reminded him of a quotation from Benjamin Disraeli, a 19th century British prime minister: "There are lies, blankety-blank lies and statistics."

Reagan pledged that he would spend the last month of the campaign sticking to the "missing issues," but, other than the economy, he did not say what those issues would be.