Union members at the BBC have voted to go on strike in protest over nearly 4,000 planned job cuts.

They will decide today when to order the stoppage — under U.K. law unions must give seven days notice of a strike, so the earliest it could come is May 20.

Some 77% of the members of BECTU — the Broadcasting Entertainment Cinematograph and Theatre Union — backed the strike call, while 84% of members of the National Union of Journalists support it.

In December BBC director general Mark Thompson said he planned to cut one-fifth of the pubcaster’s staffers and sell two divisions, BBC Broadcast and BBC Resources.

Thompson’s reforms are designed to prove to the government that the Beeb is being run efficiently.

Under the terms of a recently published pre-legislative Green Paper, the government effectively guaranteed the BBC’s license fee until 2016. It looks set to renew the pubcaster’s 10-year Royal charter, which expires at the end of 2006, governing its funding and practices.

“This is a clear signal to Mark Thompson that he is going too far, too fast, in his plans for changes,” said Luke Crawley, BECTU’s BBC organizer, on the BECTU Web site. “We’ve got an overwhelming mandate for strike action, proving that the director general is badly out of touch with his staff.”

The BBC said in an emailed statement that it wanted to continue discussions with the unions.

“Given the scale of the changes that the BBC needs to make, and that the unions have not allowed us to talk to them in order to address their concerns, we are not surprised by the ballot result, but we are disappointed,” the statement said.