The 21-year-old Frenchman, who had also gone quickest on both Tuesday and Wednesday, topped the timesheets with a lap of one minute 38.917seconds.
With track temperatures reaching a test high of 55 degrees Celsius, Vergne's time was over a second up on his previous best and also almost two seconds quicker than that managed by the next quickest driver, Mercedes GP's Sam Bird.
It also came despite Red Bull experiencing a number of reliability issues during the afternoon, which prevented them from fully completing a test of Pirelli's 2012 tyres.
Head of race engineering Ian Morgan said: "It was a frustrating day, due to a few niggly reliability issues which hampered our progress in the afternoon - but we had a good morning.
"Looking to Jean-Eric, I must say I have been very impressed with him during this test. He's not really been in our car for any length of time before this week and he hasn't made a single mistake."
Next up behind Bird was Ferrari's Jules Bianchi, with McLaren's Oliver Turvey fourth ahead of Force India's Max Chilton.
Esteban Gutierrez was sixth quickest for Sauber, however, he did bring out the red flags with a spin.
"I am very happy. This test was a really nice experience for me. I was able to push to the limit in a lot of different circumstances - with fuel loads from high to medium to low and with different tyres and compounds." Gutierrez said.
"This was obviously great to get to know more about the car. On my final lap I was pushing a bit too much and spun while on the super soft tyres."
Mirko Bortolotti (Williams) and Kevin Ceccon (Toro Rosso) were seventh and eighth respectively ahead of Alexander Rossi (Lotus) and Jan Charouz (Renault).