The number of drugs including spice found by staff in a prison has rocketed over the last five years.

In the 12 months to this March, 191 searches uncovered drugs within Rochester prison - 11 times more than five years ago.

Prison reform charity, the Howard League, says the increase in contraband, including drugs and mobile phones, in English and Welsh prisons reflects wider failings in the penal system.

Over the same period, 36% of the mandatory drug tests conducted in HMP Rochester returned a positive result, figures from the Ministry of Justice and Her Majesty’s Prison and Probation Service show.

In total, inmates failed 155 of the 434 tests conducted in the institution.

For the first time this year, the figures include psychoactive substances such as spice, the abuse of which has increasingly become a concern for prison staff.

Excluding them, 19% of tests returned a positive result for so-called traditional drugs, such as cannabis and methadone – a 55% increase on the rate five years ago.

The most common single drug type found to have been taken in Rochester was psychoactive substances, which was found in 59% of samples.

The situation in Rochester reflects the national picture, where 20% of all drug tests carried out in prisons in England and Wales were positive – meaning more than 11,000 samples were returned showing drug use.

Andrew Neilson, the campaigns director at the Howard League for Penal Reform, said that the finds of drugs and other contraband – including mobile phones, 205 of which were found in Rochester over the last year – were symptomatic of wider problems in the prison system.

He said: “The rising number of drugs and mobile phone confiscations is a symptom of the problems in an overburdened and under-resourced prison system that is failing the public.

“Where there is drug abuse there is also debt and violence, and these problems have become more severe in prisons across England and Wales as overcrowding and staff shortages have taken their toll.

“The best way to reduce the supply of drugs into prisons is to reduce the demand for them. "This means ensuring that prisons are properly resourced and prisoners are occupied with purposeful activity, such as work, education, training and exercise."

Reacting to the national numbers, Justice Secretary David Gauke said: “New psychoactive substances (NPS) are a game changer for prison safety, and these statistics reinforce the scale of the challenge.

“We are addressing this head on, and our £7 million investment in prison security will further bolster defences via airport-security style scanners, improved searching techniques and phone-blocking technology."