The Centurions moved to within a point of 20th-placed Kings Langley ahead of Saturday’s fixtures, whilst Slough’s third defeat in four left their joint managers furious and hoping for positive results elsewhere.
Jon Underwood described some of his players’ performances as “nothing short of disgraceful” as a run of six consecutive home wins came to a shuddering halt.
“We have been very good here (Arbour Park) recently, and as poor as we were in the second half against Kettering, I didn’t see this coming.
“We gave them awful goals at the start of the second half, but the most disappointing thing is what we did afterwards for the next 30 minutes.
“Some of our quality in the final third was shocking on a perfect surface”.
Underwood also called on his players to step up and produce two big performances in the final matches against Chesham United on Monday and Redditch United next Saturday.
The win was secured thanks to two quick goals from Danny Gudger early in the second half which left the Rebels stunned after a scrappy first half which Slough generally had the better of, but struggled to create openings.
Cirencester keeper Glyn Garner was required to make a save from Chris Flood with just 21 seconds played, but this was not to be a sign of things to come.
Despite playing some neat football around the edge of the box, Slough lacked the cutting edge required to break the visitors down. Gavin James saw a strike blocked by Garner after a one-two with James Dobson on 10 minutes, and then the Rebels won a series of corners which ended with an unsuccessful penalty appeal after Alan Griffin handled.
Dobson was off target twice, firstly after being teed up by James on the edge of the box, and then putting a free kick over the bar.
Late in the first half, Shaun Rowley made a crucial one-on-one save from Gudger in Cirencester’s first real chance.
Slough were caught cold on 48 minutes as they failed to deal with a long ball forward, and Gudger finished across Rowley.
Just five minutes later, Gudger added a second after an error from Nathan Smart allowed him to advance on goal and finish off a post.
Slough made changes and committed men forward but were thwarted repeatedly by a resilient Cirencester, who packed their defence and restricted them to shots from distance.
Lewis Putman replaced Nathan Webb and provided more of a goal threat, but his effort was either off target or too central to worry Garner.
Mark Nisbet had perhaps the clearest chance on 74 minutes, but he was unable to turn the ball home after Garner punched a corner in his direction, and an insipid Slough were unable to muster another chance.
Both sides now move on to must-win matches on Monday, with Cirencester hosting Weymouth and Slough at bogey side Chesham.
Cirencester Town Line up
Glyn Garner, Ryan Elliott, Ellis Dunton, James Mortimer-Jones (c), Ben Brown, Matt Coupe, Kerry Morgan (Henry Spalding), Adam Connolly, Alan Griffin (Charlie Griffin), Danny Gudger (Lewis Thompson), Dan Demkiv. Substitutes not used: Robbie James, Scott Rose.