Kevin Keehan has resigned as Lewes manager, leaving the club 19 points from safety in the Blue Square Premier.
Keehan announced his decision after Tuesday evening's 2-1 defeat against Rushden & Diamonds, which was their 14th consecutive league loss.
"It is the right time for me to go. It is not a decision I have taken lightly but I think it is probably best for Lewes," he told The Argus.
Keehan took over from Steve King as manager in April 2008.
Under Keehan's leadership the Rooks won only four out of 36 league matches and have exited all four cup competitions to lower league opposition.
Keehan added: "I have agonised over this. We have known for some while we are probably going to go down but a part of me was saying keep going, stay on and we will develop the youngsters which is what I wanted to do.
"For a club like Lewes I think that is the only way forward. We have gone down the road of paying more than other people and ultimately it doesn't work."
A club spokesman said: "It is now the time for everyone to get behind the team and the club to see what we can salvage from the season.
"The club also appeals, again, to anyone out there wishing to get involved financially or with offers of support to contact the club.
"There will be consultations with everyone in the club over the next couple of days. The club are very hopeful for the future. The season is not over yet.
"We must now regroup and go forward to rebuild the club on and off the pitch. We will firstly look at a caretaker appointment to give us time to get the right person in. There are a few names already mentioned that we will consider."
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