As the deadline approaches for final decisions on the financial and routing of the completed 100-mile Metrorail network, a leading opponent of the proposed Rosecroft raceway route in Prince George's County has raised questions about the line's environmental impact.

A planners memo circulated to officials by County Council member Francis B. Francois notes that the Rosecroft route probably would displace as many as 50 single-family homes and a Knights of Columbus Hall while an elevated portion of the line would pass within 100 feet of a Hillcrest Heights subdivision.

In an admitted effort to stir public debate, Francois, who is Prince George's Metro representative, also gave copies of the document to reporters. "It's responsible leadership to surface the issue with three new members of the council and a new county executive," Francois said yesterday. "It can do no harm."

The timing is important, Francois said, because, "if any change is to be made, it must be done in the next few weeks or it more than likely will never be done."

A regional conference on Metro financing is scheduled for this weekend in Warrenton, Va. In preparation, Prince George's Council members are to be briefed today by Metro planners on a number of issues, including the Rosecroft route.

The proposed Green Line route into southern Prince George's County has moved back and forth between an alignment that runs along the median of Suitland Parkway almost to the Capital Beltway and another run along Indian Head Highway before branching off to Rosecroft.

Last May, after intense lobbying by Indian Head Highway citizens groups and by developers and their attorneys, the council voted 9-2 to for the Rosecroft route over the so-called Branch Avenue at its intersection with Suitland Parkway.

Francois was one of the dissenters in that vote. His active role in resurfacing the issue has touched some raw political nerves in this county where the once highly touted Democratic Party organization was severely shaken by the defeats of its leaders, Winfield M. Kelly Jr. and Steny Hoyer Jr.

Kelly lost the county executive's post to Republican Lawrence J. Hogan. Hoyer's political star declined with his unsuccessful bid to be Maryland lieutenant governor.

At the time of the spring vote, it was reported that lobbying support for the Rosecroft route had come from Peter F. O'Malley, the lawyer and behind-the-scenes political power in Democratic politics.

O'Malley, whose law firm represents Rosecroft and other property interests in the surrounding area, including William E. Miller, a landowner near Rosecroft, expressed exasperation yesterday over the revival of the debate over the alignment of the Green Line, saying it had been "100 percent fully and thoroughly discussed."

O'Malley also accused Francois of putting "personal advancement ahead of the economic needs" of the county, which he said would be better served by growth along the less developed Indian Head Highway corridor.

"We all know there is a political vacuum in the county, that there is a leadership struggle going on," O'Malley said, giving his own explaination of Francois' actions.

Francois suggested that the more affluent residents of the Indian Head corridor had won out over the poorer residents the other route would serve. O'Malley called such arguments "old-fashioned political demagoguery" designed "to seize the political initiative and gain political support."

"There is no better master of political manuvering in Prince George's County than Pete," replied Francois. "One of the obvious ways of the master whose hand is caught in the cookie jar is to launch an attack on someone else."

Just before the council's 9-to-2 vote, Francois said. O'Malley met with him to say he had no part in lobbying for the Rosecroft line. "He wanted to avoid me attacking him, which I wasn't going to do anyway," said Francois.

"I absolutely did call council members, (on behalf of the Rosecraft route) there's no question about it," O'Malley said yesterday. "That's all I've got to say. You can say, 'O'Malley refused further comment.'"