Thomas went on England A tours to four countries from 1998-2000

The 31-year-old was a member of Glamorgan's title-winning side in 1997 and has taken more than 500 first-class wickets during his career.

"I'm sad to be leaving Glamorgan because they have been part of my life for 15 years but things change and when one door closes another opens.

"I've now come to Essex to further my career," said Thomas.

"They have had a lot of success recently so I'm hoping to help them win more silverware in the future.

"When I played against Essex for Glamorgan it was always massively competitive so I'm over the moon to now be joining them."

Essex skipper Ronne Irani said Thomas had a "fantastic track record".

He added: "When a cricketer like Darren Thomas becomes available during the transfer window it is an opportunity not to be missed.

"As has been seen, our bowling performances have let us down at times so Darren's arrival will strengthen us."

Thomas can also be a useful batsman and made his highest score of 138 against Essex at Chelmsford five years ago.