The High Court has thrown out an attempt by the far-right activist Stephen Yaxley-Lennon to challenge his jail conditions that have seen him segregated from other inmates.

Yaxley-Lennon, also known as Tommy Robinson, argued that segregation at HMP Woodhill in Milton Keynes, was destroying his mental health and breaching his human rights.

Mr Justice Chamberlain said there was no evidence the state was trying to “break” him and the court has heard he was being segregated for his own safety as he had a “mark [put] on his head” by other inmates.

The judge said Yaxley-Lennon’s claims of degrading treatment fell far short of the evidence needed for the courts to intervene on human rights grounds.

The activist was jailed for 18 months in October after admitting breaching a court order which had directed him not to repeat lies about a Syrian refugee.

Yaxley-Lennon was first held in HMP Belamarsh in south-east London – but he was moved after the jail received a large volume of abusive and racist emails, including threats to the governor, who is a black woman.

On 1 November, Yaxley-Lennon entered a closed wing at Woodhill and has been kept apart from other prisoners, but has contact throughout the day with officers and staff.

The court has heard he had refused an offer to move to a vulnerable inmates unit, saying he did not want to associate with sex offenders.

On Thursday, Alisdair Williamson KC, for Yaxley-Lennon, told the High Court his client had a complex form of post-traumatic stress disorder, exacerbated by attention deficit hyperactivity disorder.

He argued his client’s mental health would deteriorate and, upon his release on licence in July, he might return to substance abuse to cope.

That disclosure was a rare court admission from Yaxley-Lennon that he has been a habitual drug user.

Lawyers for the justice secretary said the segregation was neither solitary confinement or a punishment – but a carefully considered plan to keep Yaxley-Lennon safe.

Prison governors said two prisoners had been planning to assault him to “gain kudos and notoriety”.

Another tip-off suggested that an inmate serving a life sentence would kill Yaxley-Lennon if they were ever placed on the same wing.

Dismissing the case, Mr Justice Chamberlain said Yaxley-Lennon’s own barrister had accepted there was no evidence his client had been segregated “for the purpose of breaking his resistance or humiliating or debasing him”.

“On the contrary, all the evidence shows [the decision] was taken for his own protection and in the interests of preserving the safety of other prisoners and staff,” he added.

“He himself had said, when first detained at HMP Belmarsh, that he had a conflict with the followers of Islam.

“It was thus understandable the governor should be concerned that Mr Yaxley-Lennon’s presence might foment unrest or violence between Muslim and non-Muslim prisoners.”

The court heard there was no evidence Yaxley-Lennon was at risk of self-harm or suicide.

The judge ruled the inmate’s situation could not be classed as solitary confinement and did not amount to degrading treatment that would be an unlawful breach of Article 3 of the European Convention on Human Rights.

The judge said his segregation was ameliorated by him being allowed “some three hours per day out of his cell, which is more than twice the time allowed to convicted prisoners held in segregation”.

The judge also said Robinson was allowed to use the gym and shower every day, work (“albeit still on his own”), and he could speak to prison officers, healthcare staff and the chaplaincy daily, as well as having a weekly Bible study session.

He added that Yaxley-Lennon’s claims he was being denied contact with friends and family were “manifestly not well-founded”.

Some 120 people have been authorised to see him in 93 visits – more than any other inmate, the court heard.

He had two hours for visits four times a week and cancellations had related to suspected attempts by his supporters to orchestrate social media campaigning relating to his imprisonment.

Yaxley-Lennon’s High Court case had meant that an unrelated prosecution, for allegedly refusing to comply with a counter-terrorism search of his phone, had been put back months.

He is also facing prosecution having been accused of breaching a stalking prevention order.