The former Chelsea and Brentford boss departs from the Third Division club after exactly a year in charge at Roots Hall. He has also managed the club on two previous occassions.

Last Friday, it was announced that the 56-year-old Webb was standing down for two weeks to consider his future.

The day-to-day management of the squad fell to assistant manager Rob Newman in his absence, and he now takes over as caretaker boss.

Speaking at a press conference on Tuesday, Webb said: "This is something I did a couple of weeks ago.

"The people in the club have tried to talk me out of it (but) there are quite a lot of reasons why I have decided to take this course.

"There is no one specific reason but there are several reasons that it was a culmination of. "

Speculation on the cause of Webb's decision to leave is bound to focus on the club's dire financial problems and the uncertainty surrounding the proposed move to a new stadium in 2003.

"The off-the-field problems that were here when I came to the club are still here," said Webb.

"It doesn't matter how hard we all try to cut back on things and try make things better.

"I've got to be honest and say, despite my best efforts, I don't think those problems have gone away.

"Everybody has to start being aware of that. There isn't someone out there that's got a magic wand that will make this whole situation better."

Newman has already been in charge of the side once this season, when Webb was admitted to hospital for medical tests.

But Webb said that this decision to quit had nothing to do with his health.

Newman told the club's official website: "I want to pursue a career in club management and my time with (Webb) has been invaluable to my ambitions.

"For me his departure will be a massive loss as he has been a great person to learn and serve under."