Wasps (7) 10
Try: Sackey Con: Walder Pen: Walder
Worcester (8) 11
Try: Tuitupou Pens: Jones, Crichton
Crichton kept his nerve to secure a dramatic victory for Worcester
A penalty from Worcester's Loki Crichton 10 minutes into injury time handed defending champions Wasps their second loss of the Premiership season.
Worcester took the lead through a Sam Tuitupou try and Matthew Jones added a penalty to make it 8-0.
Wasps scored through Paul Sackey, with Dave Walder converting, to make it 8-7 seconds before half-time.
Walder kicked Wasps into the lead with half an hour to play but they could not pull clear and Crichton made them pay.
The post-Lawrence Dallaglio era at Wasps has got off to a difficult start and their defeat was compounded by injuries to Simon Shaw, Phil Vickery and captain Raphael Ibanez.
Worcester took the lead after 20 minutes when Josh Lewsey mis-judged Jones's high-ball and spilled it deep inside his own 22.
Tuitupou, who had over-run the original kick, pounced on the loose ball ahead of a desperately retreating Wasps defence to dive over the line.
Jones missed his conversion but slotted a penalty to extend the Worcester lead, before Wasps, who had seen Walder miss with a penalty and drop-goal, eventually found some fluency.
They worked their way into the Worcester 22 and although Tuitupou floored England flanker James Haskell with a massive blindside tackle scrum-half Eoin Reddan created a gap with a nicely angled run from the back of a ruck.
Sam Tuitupou's early try set Worcester on their way to a surprise win
He slipped a neat inside pass for Sackey to score under the posts and Walder's conversion brought Wasps back to within a point at half-time.
Wasps mounted a sustained spell of pressure after the break but their only reward was a Walder penalty.
As the half wore on Worcester gained the upper hand with Dale Rasmussen being held up over the line before the visitors spurned a kickable penalty.
When they were turned over it looked like being a costly mistake and their frustration was compounded when Chris Latham was called back for a forward pass after he had ghosted over.
However, deep into injury time England Under-20 winger Miles Benjamin caused panic in the Wasps defence and when the hosts went off their feet at the resulting ruck Crichton stepped up to leave Wasps struggling just one place off the foot of the table.
Wasps director of rugby Ian McGeechan:
"We were naive and we are making too many errors. When we do that it means we are not competitive in the league.
"It is a concern. We wanted to start with a bang and we haven't. It's unacceptable and we know that. We had a game out there for the winning and we didn't take it.
"Sometimes we are trying to play too much rugby and we need to be more patient. The new experimental laws mean you have to wait for your chances."
Worcester director of rugby Mike Ruddock:
"We deserved our victory. To beat the defending champions in their own back yard is a first for us and a significant achievement.
"I asked the boys to front up today and take responsibility for the jersey, for the club and for the fans and not be afraid to play rugby.
"Against Northampton last week we never got out of second gear but today the boys showed an intent to create things and we did that with the last play of the game."
"Well done to Loki. In the past he has taken stick before for missing last-minute kicks in front of the posts but he has been doing a lot of work on his skills."
Wasps: Lewsey; Sackey, Waldouck, Flutey, Voyce; Walder, Reddan; Payne, Ibanez, Vickery, Shaw, Palmer, Worsley, Rees, Haskell.
Replacements: Webber for Ibanez (41), Barnard for Vickery (70), Birkett for Shaw (38), Hart for Worsley (68).
Not Used: Simpson, Staunton, Mitchell.
Worcester: Latham; Pennell, Rasmussen, Tuitupou, Benjamin; M Jones, R Powell; Mullan, Lutui, Horsman, Rawlinson, Bowley, Wood, Collins, Talei.
Replacements: Crichton for M Jones (61), B Jones for R Powell (70), Fortey for Lutui (66), Tuamoepeau for Horsman (46), Horstmann for Collins (51).
Not Used: Gillies, Fellows.
Ref: Martin Fox (RFU).