Dicks leaves Heybridge Swifts after almost 18 months in charge of the non-league Essex club.
The former Liverpool defender has explained his decision stems from a reduction in budget for the squad this season.
Dicks said: “I decided to leave Heybridge on Saturday night after I was told that the already lower budget was being cut again.
“This, amongst other issues, and certain people at the club, has led me to make this decision.
“I believe the players and the fans deserve more. All the best for the season.”
In a statement, Heybridge – who are 16th in the Isthmian League North Division – said: “We can confirm that Julian Dicks has resigned from his position as first-team manager.
“We’d like to thank Julian for his time, effort and commitment during his spell in charge and wish him all the best for the future.
“Adrian Whitbread will take charge of the first team on an interim basis while the club explores its options.”
Whitbread is also a former Hammers defender.