President Reagan yesterday vetoed a bill that would have protected 50,000 acres of wild forests in Florida, but coupled the move with a statement favoring wilderness protection.

"My administration has proposed almost 2 million acres of land for designation as wilderness, and the unique natural habitat designated in the Florida bill would be particularly valuable additions to the national wilderness system," Reagan said.

Reagan said he vetoed the measure because it would have required the government to compensate four mining companies at a cost of up to $200 million for phosphate deposits in the Osceola National Forest. Environmentalists had disputed whether compensation was required.

The companies had applied for leases to strip-mine phosphate deposits in the boggy forest that spreads across the Florida panhandle. Interior Secretary James G. Watt denied the lease applications this week, an act Reagan said removed the threat of strip mining in the Osceola forest.

However, Tim Mahoney of the Sierra Club's office here contended that the veto left the Osceola open to future development and called the veto message "deceitful."

The phosphate companies may sue the government in order to reverse Watt's ruling, according to officials of one of the four companies.

A. Alan Hill, director of Reagan's Council on Environmental Quality, insisted, "The record is clear on this. Ronald Reagan does give a damn about wilderness."