The jail was designed to hold 318 inmates but the Howard League for Penal Reform says at the end of January, there were 530.
The charity also says the overcrowding leads to more violence and self-harm among prisoners, and hampers their rehabilitation.
Majority of Devon MPs back assisted dying bill
Just three of Devon's 13 MPs voted against the bill
Crime panel member calls for commissioner to resign
It's in the wake of the suspension of acting Chief Constable Jim Colwell
City footballers take time out to spread some festive cheer
Exeter stars bring joy to children in hospital
Calls for more control over spending
Many projects coming in over budget
Election cycle change thrown out in Plymouth
Annual elections will still be held in the city
Exeter man sentenced for sexually assaulting young girl
Woody Spencer jailed for 25 years
