The 30-year-old, who has made just one appearance for the Bees this season, is now free to find another club.
Brentford sporting director Mark Warburton told the club website: "We are pleased we have been able to reach an agreement with Paul.
"He can now get on with his career.
"We would like to wish Paul all the best for the future and thank him for his efforts during his time at Brentford."
- Sports & Recreation