Gov. Charlie Crist said Tuesday that he would convene a special session of the state Legislature to permanently ban oil drilling in state waters, following the massive BP oil spill that still threatens Florida's tourism lifeblood, the coastline.

Republican legislative leaders slammed the special session as "political posturing" by Crist, who is running an unconventional no-party-affiliation campaign for U.S. Senate.

The session could happen the week of May 24-28, Crist told reporters at the Capitol. The issues: a constitutional amendment banning oil drilling, and legislation to promote clean and renewable energy sources in Florida, such as wind and solar.

If approved, the drilling amendment would appear on the Nov. 2 ballot and would apply to state waters 3 to 10 miles from shore. It would not affect federal waters farther out. The amendment would need 60 percent voter approval to become law.

"I'd like to do it sooner rather than later," said Crist, who supported drilling in state waters just last year. "People are concerned about it. I sense it."

Crist, who quit the GOP last month, is putting Republican legislative leaders in a tough spot. Even as they seethe at the governor and his motives, voting against the drilling ban would be politically risky with oil polluting the Gulf of Mexico. Indeed, Crist said "nobody reasonable" would vote against the ban and predicted it would pass easily.

House Republican Leader Adam Hasner, R-Boca Raton, said "a call for a special session is purely political." He noted that state law already bans drilling in state waters and "no one is trying to change that."

"That is transparent political posturing by Charlie Crist," he said. "Right now, the issue is protecting our environment and protecting our economy. A constitutional amendment is about Charlie Crist protecting his political future."

A special session costs about $40,000 a day, to bring legislators and their staffs to Tallahassee.

"I resent the fact of being used as a prop in his U.S. Senate campaign," said Sen. Carey Baker, R-Eustis. "Either way, he wins. This is cold political calculation on his part. If we do nothing, he bashes us. If we give in, he can claim to be the gallant leader protecting Floridians."

Florida has outlawed drilling in state waters since 1990, but the oil industry has been lobbying heavily for two years to change that. Big Oil came close in 2009, when a drilling bill passed in the House. The effort stalled in the Senate due to opposition from Senate President Jeff Atwater, R-North Palm Beach.

But on April 20, a game-changer happened: The BP oil rig off the Louisiana coast exploded and, two days later, sank. Four million gallons of oil have spilled into the Gulf. None has reached Florida shores, but state officials are bracing for a potential impact.

Sen. Dan Gelber, D-Miami Beach, said Florida needs better protections than a state law legislators can change at any time. Public sentiment on drilling shifts frequently. Just a few years ago, gas topped $4 a gallon and the catch phrase was "drill, baby, drill."

"Anyone who thinks the oil industry is going to back down forever is absolutely mistaken," Gelber said. "As soon as there is an opportunity to push oil drilling, an army of lobbyists will descend upon Tallahassee again. If it's not in the constitution, they absolutely will bully it through the Legislature, as they almost did last year."

The constitutional amendment needs a three-fifths vote from both chambers to be placed on the ballot. Complicating matters: The relationship between Crist and Republican legislators grows more hostile by the day since the governor bolted the party to avoid certain defeat in the U.S. Senate primary against Marco Rubio.

Still, even if Republican legislators are loath to support the constitutional ban or give Crist a political victory, they would be hard-pressed to vote against it with a busy and unpredictable 2010 election less than six months away.

"I certainly think it has a much better chance of passing the House now than ever," said House Rules Chairman Bill Galvano, R-Bradenton, who has opposed past attempts to open state waters to drilling. "With what has occurred with the spill, a lot of people are re-evaluating the issue."

Crist also could add complicated and controversial renewable energy legislation to the special session agenda. That issue would bring hordes of utility lobbyists into the mix. A dramatic shift to cleaner sources of fuel would mean higher power bills for Floridians.

Crist hasn't outlined a specific clean-energy proposal but said he wants to "look at things that wouldn't drive up rates — tax cuts, incentives, things like that for the utilities to use more solar, wind and nuclear."

Staff writers Julie Patel and Aaron Deslatte contributed to this report.