Wielding blood-drenched chains with razor-sharp knives attached, a group of hardline Muslims flay the skin from their backs as a baying crowd looks on, chanting and beating their chests.

With the force of each new sickening swing of the bladed instruments, more blood spatters through the air, landing on a plastic tarpaulin on the ground – and even on the faces of some of the audience.

This ‘barbaric’ practice has been banned even in ultra-religious Iran by the supreme leader Ayatollah Khamenei. However, these appalling scenes did not take place in Iran, Iraq or anywhere else in the Middle East – but in suburban Britain, and partly on local council land.

Gruesome: Images from the video show men whipping their backs, sending blood flying over the crowd

The Idara-e-Jaaferiya mosque in Tooting, South London (pictured), where a breakaway group of 14 named individuals were banned from carrying out the practice

A long-running legal battle over the ritual self-flagellation, known as zanjeer zani, came to a head in court last month when an order was granted banning a breakaway group of 14 named individuals from carrying out the practice within a mile of the Idara-e-Jaaferiya mosque in Tooting, South London.

These graphic images from a video, discovered by The Mail on Sunday, show the event in 2013 when a violent confrontation between the different factions at the Shia mosque, which is directly opposite a church, led to the legal action.

We've been trying to get this stopped for years

According to the mosque authorities and their supporters, the breakaway group staged the blood-letting each year without permission.

The eight-minute video shows a succession of men feverishly thrashing themselves over each shoulder in turn with the sharp ‘whips’, each of which carries five curved blades. Each man chants incessantly the name of Imam Hussein, the Prophet Mohammed’s grandson.

Hussein was killed in a 7th Century battle in Karbala, Iraq, and the zanjeer zani is a way of mourning the anniversary of his death, known as the Day of Ashurah. One man in the video, suffering the most severe injuries, appears to be senseless with pain, but when others move in to stop him inflicting more wounds, he fights them off and continues.

In an earlier incident, a marquee was erected next to the mosque over some pay-and-display parking spaces, apparently with the permission of Wandsworth Council, where more flagellation took place.

The practice is far from universal among Shias and has been the subject of heated debate throughout the Muslim world. Similar ceremonies continue in a handful of other Shia mosques around Britain.

A man tries to stop a participant from inflicting more pain. Massoud Shadjareh, of the Islamic Human Rights Commission, has condemned the barbaric practice

Massoud Shadjareh, of the Islamic Human Rights Commission, condemned it, saying: ‘This is a barbaric practice and should not be allowed for all kinds of reasons, not least health-and-safety grounds because of the blood that is flying around and the danger of cross-infection from the implements.

‘The committee running the mosque had been trying to get this stopped for years, but no one would help them, including the police and the council and the local MP Sadiq Khan, as they were always told it was on private premises and a religious matter. Everyone treats it with kid gloves because of the sensitivities.

‘But the truth is there is no obligation upon Muslims to do this. In 2011, Wandsworth even let them erect a tent next to the mosque over council parking spaces.’

When the MoS visited the Idara-e-Jaaferiya mosque this weekend, two clerics, who did not want to be identified, said the zanjeer zani ritual took place in the main prayer hall of the mosque, but had now stopped.

They confirmed that the footage was taken in the main prayer hall, used during large gatherings such as Friday prayers, and that the green carpet of the main hall had to be changed as it became contaminated with blood, despite the attempts to protect it with plastic sheets.

One of the men named in the court documents, 47-year-old businessman Nadeem Abbas, defiantly predicted that others may well continue the rite when the Day of Ashura next comes around in October.

Mr Abbas claimed the flagellation issue was being used as an excuse to silence those who criticised the way the mosque was being run. He said: ‘This is a political dispute more than a religious one. They didn’t like the fact we were handing out leaflets and questioning the committee’s decisions, so they chose flagellation as the way to ban us from the mosque, but now we’re allowed back in.

‘Only the named people are banned from practising it in the mosque – others may well take part next time the Day of Ashura comes around. This ritual is allowed in the Shia religion. I’ve only done it myself when I was 18, but I respect other people’s right to do it.’

The marquee erected over the car park: A marquee was erected next to the mosque over some pay-and-display parking spaces, apparently with the permission of Wandsworth Council, where more flagellation took place

Shias make up less than ten per cent of the world’s 1.5 billion Muslims. In Britain, the Shia population is believed to be about five per cent of Muslims, and the Idara-e-Jaaferiya mosque is mainly used by Shias from Pakistan.

Self-flagellation is also a rarely observed Christian tradition. In the 13th Century, a group of Roman Catholics – known as the Flagellants – went to extreme ends.

They were later condemned by Rome as a cult, but the practice continues among some Catholics in the Philippines and Mexico. Some members of the Catholic lay organisation Opus Dei also practise milder self-flagellation using a whip of knotted cords.

A Wandsworth Council spokesman said: ‘We would be concerned about the public-health implications if this form of worship were to take place, and if so, we would want to work with the local community, the police and other agencies to ensure that the risk to public health was minimised.’ The mosque authorities declined to comment. A Metropolitan Police spokesman could not immediately comment on the row, but added: ‘The Met will always investigate any allegation of crime reported to us.’

Last night, Tooting MP Sadiq Khan, the Labour candidate in May’s London Mayoral election, condemned the practice.