An investigation has been launched after photos emerged of inmates showing off smuggled steaks and takeaways inside a Dorset prison.

The pictures which were taken on an illegally-possessed mobile phone inside HMP Guys Marsh, near Shaftesbury, and posted to social media, also appeared to depict drug possession.

North Dorset MP Simon Hoare said he was "very concerned" at the photos, which were allegedly posted on an Instagram account.

They came to light after a builder was mistakenly added to a Facebook group by a prisoner.

Mr Hoare said he would be seeking an urgent meeting with the governor, Her Majesty's Inspectorate of Prisons and government ministers.

The images emerged in a turbulent week for the Ministry of Justice after it was forced to obtain a High Court injunction to order staff back to work after a mass walkout over health and safety fears.

A Prison Service spokesperson said of the images: "This behaviour is unacceptable. We will be referring this matter to the police for investigation and have had the social media profiles removed.

"We are stepping up measures to find and block mobile phones in prisons and those found with them face extra time behind bars."

It is believed that four of the six prisoners who were pictured in the social media posts have been moved to other prisons.

In the HM Inspectorate of Prisons' latest report, inspectors said staff had "all but lost control" of the Category C jail.

Just yesterday, MP for South Dorset addressed the House of Commons over the state of the country's prisons and the staff walk-out.

Whilst he said he did not agree with the walk-out, he said: "[With] The increased workload, lower morale, poor leadership in some cases, a higher retirement age and an increased risk of being assaulted have all contributed to the problems we see today. Frankly, who can blame the officers?

He added that spice is 'endemic' and brought in to prisons 'via drones and social visits, thrown over prison walls, brought in by new or returning prisoners and, apparently, by soaking letters in it. As I said, drugs lead to bullying and debt, increasing the risk to both prisoners and officers.'

He called on the government to hire more officers and use regular dog searches to restore some order in jails.

He also said he is concerned that courts do not take assaults on prison staff as seriously as they do assaults on police officers.

"A prisoner who was due to be released the next day “potted” a female prison officer. “Potting”—I apologise for being so crude—involves urine and excrement being thrown over an officer. It is disgusting, demeaning and outrageous. That prisoner was released the next day, when he was arrested for assault, fined £200 and given a suspended sentence. That is farcical.

"In another case, another female officer was “potted” and the prisoner received a mere 21 extra days on his sentence. That officer was then goaded and teased by the prisoner when she returned to work. Again, that is unacceptable. Perhaps because “potting” causes no physical damage, the courts tend to be more lenient, but the effect on officers who have been subjected to such disgusting humiliation is traumatic, and offenders should be dealt with harshly.

"The prison population is becoming more violent, with the number of those sentenced for violent offences rising by 30% in the past 10 years. Officers are clearly struggling to cope on many occasions, and their concerns have been expressed in a number of ways to me personally and by taking the action which I did not agree with, but which many of us understand. A survey of Prison Officer Association members in 2014 found that the demands of the job are particularly high and support from managers is low. I am not commenting, as I said, on any prisons in my constituency, but we had a saying in the Army that there are no bad soldiers, only bad officers. I suspect that that is true in every walk of life and I am sure it applies in the case of prison staff."