Two members of the Prince George's County Council who opposed previous efforts to modify TRIM, the county's tax-limiting charter amendment, yesterday introduced legislation that would place the question on the ballot for a third time.

Council members Anthony Cicoria and Sue V. Mills stole the spotlight from their legislative colleagues by proposing a thaw of the four-year-old tax freeze, saying the county will need additional tax money to pay for services for future residents.

Mills was the only member of the council who opposed last year's unsuccessful attempt to get voters to modify TRIM, the most restrictive tax freeze in the nation. Cicoria was elected to the council last year campaigning as a supporter of TRIM opposed to modification.

Under TRIM (Tax Reform Initiative by Marylanders), the county can collect no more than the amount of property tax received in 1979, about $143.9 million. Cicoria's bill, cosponsored by Mills, would allow the county to raise the ceiling annually by the amount of property tax on new development, a solution long favored by many TRIM critics.

The latest attempt to ease the provisions of TRIM would appear on the ballot in November 1984. The county's voters, urged on by Mills and Cicoria, decisively rejected a more far-reaching effort at modification last year.

While some form of modification is certain to win support of the all-Democratic council, members who have long been in favor of changing TRIM said Cicoria's move was ill-timed, and suggested that it was an effort to get publicity. They criticized Cicoria's decision to introduce legislation before a citizens' task force, appointed by the council earlier this year to review the county's financial problems, has had a chance to deliver its report.

"We as a council agreed that we would not come up with any ideas of our own or any proposals until we heard from the task force," said council member JoAnn Bell.

"We don't want to upstage one of our own committees," council member William Amonett, who proposed the task force, told council chairman Frank Casula.

Mills countered by saying, "You know as well as I do that the purpose of these task forces is to cause delay. This will cause action."

Cicoria said he became convinced of the need to modify his earlier stance because of recent publicity detailing TRIM's negative effects. Mills said cosponsoring the proposal is not a change in her position, that she would have backed such a proposal all along.

Last year's proposal called for not only the addition of new construction taxes to the TRIM ceiling but for an additional 4 percent yearly increase at the discretion of the council.

TRIM coauthor William Goodman was unmoved by yesterday's development, saying he will continue to oppose any effort to modify TRIM.

"There's no additional revenue needed at this time," he said. "We don't have residential developmment that pays for itself now. All it does is increase the burden on everyone else."

Though Cicoria's bill is the first to be introduced by an elected official, other groups have been working on proposals to modify TRIM.

In addition to the County Council task force, County Executive Parris Glendening has appointed a group headed by a former Chamber of Commerce president, and a coalition of leaders of public safety workers' unions is also drafting a proposal.

Glendening said yesterday he hopes to have a measure, whether his or Cicoria's, approved by the middle of December.