A controversial proposal that proponents say would allow rapidly growing Loudoun County to preserve its dwindling farmland was approved yesterday by a Virginia Senate committee.

The Committee on Local Government voted 10 to 4 to send the bill to the full Senate, despite reservations expressed by opponents who warned that the measure would be too cumbersome for local officials to monitor.

The legislation would enact and expand in state law a right that Loudoun County has contended it already has.

The bill grows out of a lawsuit over the Countryside housing development in eastern Loudoun, where a group of homeowners are challenging the county's decision to allow more housing than was originally proposed.

The county contends it can increase the density of housing at Countryside in exchange for allowing land in western Loudoun to go undeveloped.

Proponents say that transferable development rights would help preserve farmland while benefiting developers by allowing them to build more densely in already-populous areas of the county.

"Owners of land in the designated rural areas would be allowed to separate the right to develop from the land itself and sell that right to owners of the land in the developing areas," according to Sen. Charles L. Waddell (D-Loudoun), a sponsor of the development transfer rights bill.

The issue has sharply divided legislators, as well as Loudoun officials.

"Who's going to determine who's going to get how many development rights?" asked Sen. Wiley F. Mitchell Jr. (R-Alexandria).

He added, "The county is almost artificially creating wealth."