The supply of heroin is "abundant" in some Scottish jails, according to a report produced for the prison service.
Inmates said officers often ignored drug use in Scottish jails
Some inmates claimed they could "get anything" in jails, with heroin among the most widely-used drugs.
Some of the prisoners claimed that drug testing could actually lead to first time heroin use because it does not stay in the body as long as cannabis.
The Scottish Prison Service (SPS) insisted it was not complacent about the problem of drugs in prisons.
Researchers spoke to both inmates and prison staff.
They found that some staff felt limited in what they could do about drug use and a number of prisoners reported officers turning a "blind eye".
The Conservatives' justice spokeswoman Margaret Mitchell told the BBC's Good Morning Scotland programme: "This report is much more alarming than we can possibly imagine.
"The general public have a right to expect that prisons should be drug free and every effort should be made to ensure that these prisons are drug free.
"We have to look at every instance where drugs are smuggled into prisons and put a block on that."
She said there were problems with understaffing, low morale and a "resigned attitude" to drugs in prisons and that there needed to be more prison rehabilitation programmes.
She also said it was "outrageous" that prisoners had access to mobile phones, enabling them to contact people outside.
"If there needs to be more sniffer dogs or glass partitions to stop drugs being passed over during visiting, then so be it. We have to get on top of this."
Andrew Fraser, director of health and care for the SPS, said some of the concerns were already being addressed.
He said a lot more resources had gone into counselling support and the medical and nursing aspect.
"We know the majority of people who come into prison have an addiction, mostly heroin but usually a cocktail of heroin with other drugs and alcohol."
He added that heroin did not stay in the body as long as cannabis and was easier to bring into prison and conceal.
"The prison drug problem reflects what's going on outside in the community and heroin is a very prominent drug," he said.