Taiwo Awoniyi marked his 100th Forest appearance with the early opener at Stamford Bridge and Igor Jesus’s penalty doubled their advantage soon afterwards.
Cole Palmer compounded Chelsea’s misery when he missed a penalty late in the first half.
Awoniyi struck again after the interval and Joao Pedro’s eye-catching bicycle kick in the closing stages was no consolation for lacklustre Chelsea.
Languishing in ninth place, Chelsea’s wretched run has left them on the verge of failing to reach next season’s Champions League.
Chelsea have lost six consecutive league games for the first time since 1993.
Scoring for the first time in six league matches was the only positive in a shambolic display.
Calum McFarlane’s team are 10 points behind fifth-placed Aston Villa, with only nine points available in the race for the top-five finish that secures Champions League qualification.
However, sixth will also earn a Champions League berth if Villa finish fifth and win the Europa League, leaving Chelsea – currently four points adrift of sixth-placed Bournemouth – still with a slender chance.
Forest’s third successive league victory moved them six points clear of the relegation zone, with four more points needed to guarantee survival.
There are just three games left for each club in Forest’s scrap with fourth-bottom Tottenham and third-bottom West Ham.
Pereira made eight changes from Forest’s previous league game as he prioritised holding onto their 1-0 lead in Thursday’s Europa League semi-final second leg at Aston Villa.
The gamble paid off and Pereira’s side, unbeaten in their last 10 games in all competitions, can now focus on finishing off Villa to reach their first European final since 1980. (AFP)
