The judge in the case of paedophile headteacher Neil Foden was "incorrect" to say he would spend at least 11 years in prison, according to the Crown Prosecution Service.
In a letter sent to Plaid Cymru MP Liz Saville Roberts, the CPS said Foden can in fact be released after serving just half his sentence.
Foden was jailed for 17 years in July for sexually abusing four girls over a four year period.
Saville Roberts has asked the UK government to look at the case, saying victims "live in fear" of his early release.