Worthing Football Club fell to a first Ryman League Premier Division defeat in nine matches at Woodside Road this afternoon.
First-half efforts from Byron Lawrence and Tom Bullard, plus a late Matt Blake strike, helped fourth-placed Leiston to a 3-1 victory.
Worthing were much-improved in the second half, with Sam Rents pulling a goal back 12 minutes from the end. As well as Rents' goal, the home side had strong appeals for a penalty waved away by referee Leigh Crowhurst.
Despite the defeat, Worthing stay eighth in the standings but are now four points off the play-off places.
After a quiet opening ten minutes, Jack Fagan was called into action. Gareth Heath's fierce 25-yard free-kick had to be tipped wide for a corner. Worthing failed to clear their lines from the resulting corner, with the ball falling to Byron Lawrence on the edge and his deflected effort fired Leiston in front.
The home side responded well after falling behind and had a couple of opportunities before 20 minutes were out. First, Will Hendon's volley from the edge was straight at Jacob Marsden in Leiston's goal. Then, Kane Wills worked some room down the right, before pulling back for Omar Bugiel but his goalbound strike struck team-mate Lloyd Dawes.
Worthing were once again undone by a corner on 23 minutes. Heath's delivery was met by Tom Bullard who headed home - despite Harvey Sparks' attempt to clear on the line.
Great work from Dawes saw him dispossess Lawrence eight minutes prior to the break, her then beat two defenders, only for his shot to be blocked. Dawes then dragged an effort just wide of the far post three minutes later.
Heath and Niko Muir exchanged passes with the former then flashing a 20-yard strike just wide as Leiston went in a the interval two goals in front.
Leiston made a fast start to the second and nearly added a third three minutes after the break. Patrick Brothers' cross was met by Matt Blake but his header struck the bar.
The visitors continued to probe as Ollie Brown's cross found Brothers, though, he skewed a shot wide on the hour.
Substitute Brannon O'Neill's long-ball found Bugiel but he could only head wide as Worthing looked for a way back into it.
Worthing felt they should have been awarded a penalty 20 minutes from time. Bugiel took the ball in his stride, then went down under a Bullard challenge, only for referee Leigh Crowhurst to wave play on.
Leiston contiuned to carry a threat with Muir coming close to netting a third on 71 minutes. He controlled, before turning and seeing a shot from the edge go just wide. Worthing found dealing with corners an issue all day, with Jake Hutchings' free-header going just over four minutes later.
Worthing then had hope 12 minutes from time as Sam Rents pulled a goal back. After riding a challenge, Rents' swivel and shot looped over Marsden into the top corner.
With Worthing piling men forward in the closing stages, Blake was sent clear seven minutes into stoppage-time, before slotting past Fagan to seal all three points for Leiston.
Worthing are back in action on Tuesday as they travel to National League side Sutton United for their FA Trophy second-round replay (7.45pm)
WORTHING: Fagan; Hendon, Boiling, Heath, Rents; Edwards, Wills; Hopkinson, Bugiel, Sparks; Dawes. Subs: O'Neill (Edwards, 60), Brodie (Hopkinson, 45), Watson (Hendon, 89), Schneider.