Barrow have become the first club to be relegated from the Kingstone Press Championship.
The Raiders suffered an eighth straight defeat, going down 34-14 at Dewsbury on Sunday, and are now 21 points from safety with just five matches left.
First-half tries from Nathan Mossop and Craig Briscoe gave Bobbie Goulding’s men some hope of pulling off a surprise win but Ewan Dowes and Kieran Hyde both scored two tries as Dewsbury maintained their challenge for a top-five finish.
With five clubs going down to Championship One to make way for the new domestic structure in 2015, even champions Sheffield Eagles are not safe, especially after losing 28-18 at home to Batley.
The Bulldogs made a dream start with tries from Wayne Reittie and Ben Heaton inside seven minutes and, although the Eagles pulled tries back through substitute Will Hope and Menzie Yere, forward Jacob Fairbank - playing on a dual-registration from Huddersfield - crucially touched down for the visitors on 56 minutes before winger Alex Brown made sure of the win two minutes from the end.
Leigh maintained their 10-point lead at the top of the table thanks to a 72-22 win at Rochdale.
Cameron Pitman scored a second-half hat-trick of tries, two came from both Gregg McNally and Tom Armstrong while Sam Barlow, Liam Kay, Matt Sarsfield, Sam Hopkins and Ryan Brierley also touched down, with Martyn Ridyard kicking 12 goals.
Rochdale scored twice in the first 10 minutes through Gareth Langley and St Helens winger Adam Swift but the game was over by the time Jordan Case and Anthony Walker got their other tries.
Featherstone stay second after scoring six tries in a 35-24 win over Whitehaven at the Recreation Ground.
Rovers scorers were Will Sharp, Ian Hardman, Jason Crookes, Andy Bostock, Greg Worthington and Gareth Moore, who also kicked five goals, while Jamie Rooney rounded off the scoring with a drop goal on his first appearance since returning to his home-town club.
The Cumbrians led 22-16 at the break thanks to two tries from veteran winger Craig Calvert and others from Scott McAvoy and Mark Foster but they needed a last-minute penalty from Tommy Carr to earn them a losing bonus point, which could prove crucial in their battle to avoid the drop.
Halifax remain in touching distance of Featherstone after extending their unbeaten run to seven matches with a 48-30 win at lowly Swinton.
Ben Johnson’s tries either side of half-time proved crucial for the visitors, whose other touchdowns came from Paul Mennell, Tommy Saxton, Gareth Potts, Scott Murrell, Luke Adamson and Ross Divorty, with Steve Tyrer kicking eight goals.
Ed Barber, Brad Dwyer, Kevin Penny, Luke Menzies and Mike Morrison scored tries for the Lions, with Mick Nanyn kicking five goals.
Doncaster’s hopes of claiming a top-two finish were dealt a major blow when they went down 44-32 to Keighley, who thereby kept alive their survival hopes.
James Haley scored a hat-trick of tries for the Cougars, while Scott Law touched down twice and other tries came from James Craven, Richie Barnett and Danny Jones, who also kicked six goals.
Doncaster, who had won their previous four matches, scored tries through Kyle Kesik, Richard Wilkinson, Mark Castle, Nev Morrison, Ben Crooks and Sanderson, who also kicked four goals.
Workington also boosted their battle to avoid the drop when they extended their winning run to six matches by edging out North Wales 12-8 at the Racecourse Stadium.
When Jonno Smith crossed for a try on 72 minutes it looked to have sealed a first win for coach Anthony Murray but Graeme Mattinson went over in the last minute to seal the points for the visitors.
Dom Speakman had scored the only try of the first half to give the Crusaders a 4-0 lead but Brett Phillips equalised on 57 minutes and Carl Forber’s conversion put Town in front for the first time.