A white supremacist behind the “Punish a Muslim Day” campaign has been jailed for 12 and a half years.

David Parnham, who called himself “Muslim Slayer” and sent packages containing fake anthrax, is to serve his sentence in hospital until he is well enough to be transferred to prison.

The Old Bailey heard the 36-year-old had launched several waves of malicious letters targeting mosques, the Queen and politicians including David Cameron and Theresa May.

He admitted offences including soliciting murder, encouraging crime, bomb and noxious substance hoaxes and sending letters with intent to cause distress.

In early 2018, a series of typed “Punish A Muslim Day” letters were sent out to encourage violence on the date of an American white supremacist’s birthday.

The letters claimed Europe and North America was being “overrun” by Muslims and contained a makeshift scorecard for attacks ranging from pulling off women’s headscarves to acid attacks, torture, bombing a mosque and “butchering” Muslims with guns, knives and vehicles.

Judge Anthony Leonard QC said Parnham had been suffering from an autistic spectrum disorder but rejected the suggestion he was psychotic at the time of the offences.

“You have yet to appreciate the seriousness of what you have done and seem to want to return to the community at the earliest opportunity to live with your parents,” he told the court on Tuesday.

Parnham’s failure to appreciate the harm he caused to the Muslim and wider community meant the risk of reoffending was greater, the judge said.

The court heard that although no violence was linked to the campaign, it sparked widespread fear in Muslim communities across the UK after being received by politicians including the then home secretary, Sajid Javid.