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.
Alison Hernandez secures third term as police and crime commissioner
She'll continue tackling major issues on her to-do list
How Exeter's traffic troubles influenced council vote
LTN campaigner ousts Labour candidate
Labour tightens grip on Plymouth City Council power
They've gained nine extra seats
Radio Exe newsreader to abseil down Exeter Cathedral
Josh Tate will descend over 100 feet on Saturday
Labour retains control of Exeter City Council
Despite losing a seat to the Greens and an independent
Colyford pushes for more action in ongoing spat with Colyton
East Devon District Council's been asked to intervene
