Irani has enjoyed great success with Essex in 40-over cricket

The 35-year-old ex-England all-rounder was set to quit at the end of the season because of a knee problem but has decided to bow out now.

Irani, who has been plagued by knee problems in recent years, has not played since mid-May and needs surgery.

"It's a bitter pill to swallow because I'd hoped to get used to the idea of retirement before it came," he said.

I'm going for an operation in July and that's my lot I'm afraid Ronnie Irani

"I had a nasty twist and fall against Leicestershire and the knee hasn't recovered since.

"It's been a tough decision. I have been able to manage the pain in the last few seasons but this latest injury is more acute, it's really bad and I can't continue.

"If I'd done it 10 years ago I'd have been out of the game sooner. I'm going for an operation in July and that's my lot I'm afraid."

Essex offered Irani a new two-year contract earlier this year but he rejected it, saying: "My right-knee condition is so acute that I would be kidding everyone if I accepted it.

"I'm immensely disappointed but I've loved every minute of my time here."

Irani, who was made Essex skipper in 2000, made 31 appearances for England's one-day side and played in the 2003 World Cup.

And, after leading the county to the 40-over league title for the last two seasons, he hopes supporters will look back on his time with Essex fondly.

"I want to make sure that every one of the club's supporters will say that Ronnie Irani gave everything and that he never took a penny without performing," he said.

"Since I gave up bowling in 2003, my batting has really come on but my deteriorating health means that there is no realistic chance of me playing a meaningful role in the 2008 or 2009 seasons."