The prison service has hit back at a prisoner's claims of rampant drug abuse at HMP Bullingdon.

Last week, Morgan Thackwell, a 23-year-old from Marlow, provided an insider account of life at the prison.

He said he had witnessed episodes of violence and self-harm - and also spoke of a flourishing drug trade behind bars.

Mr Thackwell estimates that up to half of his fellow inmates are users of spice, the potent 'zombie drug.'

A spokesperson for the prison service has responded to these allegations, emphasising that the authorities take a zero-tolerance approach to drugs in jail.

They stated: "We do not tolerate drugs in our prisons, and HMP Bullingdon has substance misuse professionals on hand and an Incentivised Substance-Free Living Wing to support the recovery of former drug users.

"More widely, we have invested £100m into tough security measures across the prison estate, including X-ray body scanners and more specialist sniffer dogs to stop the flow of drugs entering jails."

HMP Bullingdon is a men's prison located in Arncott, Oxfordshire - just over the border from Buckinghamshire.

It is a Category B establishment, housing inmates that are not assessed to be 'high-risk.'

The prison opened in 1992, and its maximum capacity is believed to be around 1,000.

In a letter sent exclusively to this newspaper, Mr Thackwell - who is awaiting trial on drug and weapon charges - made a number of allegations about conditions at the prison.

He said: "I was informed by staff when I arrived here that the prison holds a maximum of 1,000 people - a laughable, blatant lie. Every single-man cell has been turned a two-man cell."

He claimed that inmates are locked in small cells for much of the day, around two metres from toilets that are frequently blocked.

Some of Mr Thackwell's most shocking claims related to the prevalence of drug abuse inside the prison.

He said of this: "There have been 22 seizures from spice since I have been here, and that's just on my wing.

"I have been two-and-a-half weeks in this prison. Long-term prisoners say it's been this way for years.

"There's a dark humour in spice addicts dancing down the wing, incoherently singing with baggies filled with spice, sheets in their hands.

"However, this is someone's brother, uncle, father, husband, cousin ... and they need serious help, not ridicule."