Old Elthamians ran in seven tries - including four in the last 20 minutes - to send Raiders to a 51-21 home defeat.
Second-bottom Worthing had turned around a 20-13 half-time deficit to open up a 21-20 lead ten minutes after the restart, before a late collapse.
With fourth-from-bottom Barnes picking up a losing bonus-point at Henley Hawks, Raiders are now four points from safety with seven games to go.
Old Elthamians were off to a flying start getting the first try inside six minutes. Kariym Irving failed to handle inside his own try area, with Dominic Lespierre on hand to take advantage. William Robinson then added the extras to put his side 7-0 ahead.
Raiders responded well and had their first points of the day less than a minute later courtesy of Matt McLean's penalty.
Robinson was causing Worthing's defence all sorts of problems and went over after 20 minutes. Clever work saw him dodge a challenge then bundle over, before converting his own try to make it 14-3.
Once again the home side showed great resilience, responding almost immediately once again. McLean raced away, before his clever reverse pass sent Loosmore clear and he secured Raiders' first try less than five minutes later.
Robinson crashed over two penalties in the space of as many minutes just after the half-hour, then McLean converted one for the home side as Worthing went in 20-13 down at the interval.
Raiders got off to a blistering start in the second, running in eight unanswered points to take the lead for the first time within ten minutes of the restart. A converted Dino Lamb try, coupled with McLean firing over a penalty put Worthing 21-20 ahead before 50 minutes were up.
Raiders' task was made harder as Harry Forrest was shown a yellow five minutes later, then a collapse ensued in the final 20 minutes.
George Meesum forced his way over following a scrum on the hour as Old Elthamians went back in front.
Third-placed Elthamians made the most of their man advantage, running in a second try in Forrest's absence with 15 minutes left to play. A surging run from Christopher Surman saw him work some room, then his reverse pass sent Lespierre running away for his second try of the afternoon.
Raiders matched high-flyers Old Elthamians for long periods before they pulled away in the closing stages. A converted penalty try, plus Lespierre's third of the day put them firmly in control. With the final play, replacement Jay Rudland-Thomas went over in the corner as Raiders fell to a heavy 30-point defeat.
Worthing welcome fourth-placed Taunton Titans to Roundstone Lane for a third home game in as many weeks next Saturday.
RAIDERS: Gatford, Watson-Brooks, Sargent, Lamb, Lake, Whittall, Hewick, Perkins; Leeming, McLean, Irving, Loosmore, Richards, Coxon-Smith, Forrest. Replacements: Harris, Finney, Barlow, Boyland, Dobson.
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