Convicted child killer Susan Smith should not be paroled, because her bad behavior in prison included performing sex acts and doing drugs … so says the former correctional officer with whom she hooked up.

Alfred Rowe, the disgraced prison guard previously employed at Camille Graham Correctional Center in South Carolina, tells TMZ … Susan is not ready to be released.

Smith becomes eligible for parole in early November for murdering her two children, Michael and Alexander, according to a South Carolina corrections official.

The ex-guard admitted to us the sex with Smith wasn’t worth losing his job or his reputation.

Rowe says he “allowed” Smith to give him oral sex 2 to 3 times, but she asked for nothing in return. Prison authorities caught wind of their affair and fired Rowe.

He went on to say Smith is “not ready for parole” due to her truckload of disciplinary infractions over the years — many for drug-related offenses. He noted her infraction record was among the worst he had ever seen.

Rowe even thinks Smith will eventually wind up behind bars again for drugs if paroled this fall. The only way he’d support her possible parole is if Susan proved she had been clean for a long period of time.

Alfred makes it clear his negative opinion of Susan has nothing to do with their complicated relationship. Rowe pleaded guilty in 2001 and was sentenced to 5 years probation over his sexual affair with Smith.

While Smith is eager to shorten her life sentence — which she received for murdering her 2 young sons in 1994 — Rowe says she is actually revered among other female prisoners.

This was a shock to Alfred, who said in most cases, people who hurt children are seen as the worst scum by the rest of the inmate population.