Image caption In July a Sikh woman and her Christian husband were locked out of their own wedding in Swindon

Sikh weddings are regularly disrupted by protesters opposed to mixed-faith marriages in gurdwaras, a BBC Asian Network investigation has found.

Victims and their families have accused the protesters - who believe non-Sikhs should not be getting married in Sikh temples - of threatening behaviour.

In some cases, protesters have barricaded themselves inside gurdwaras to prevent ceremonies taking place.

Last year the windows of a family's house in Coventry were smashed.

The incident took place just hours before a mixed faith wedding in a nearby gurdwara.

The father of the bride told BBC Asian Network the house was targeted because his daughter was marrying a Hindu in a Sikh temple.

He said: "Some of these people didn't want the wedding to go ahead. This was the way for them to frighten me."

The couple ended up having a police escort for the wedding.

Media playback is unsupported on your device Media caption 'Kiren' explains why she married her Catholic fiancé in secret in December 2012

In July a Sikh woman and her Christian husband were locked out of their own wedding in Swindon.

More than 40 protesters had barricaded themselves inside the gates of the Sikh temple.

The bride's mother pleaded with the men to call off their action but the gates of the gurdwara remained shut.

One of the protesters, speaking anonymously to the BBC Asian Network, said: "The last thing I want is to go to a gurdwara and cause trouble. I can say hand on heart that we have never resorted to violence. We don't want to do this."

'Don't use our guru'

But he said he believed it was hypocritical for a bride or groom to go through a ceremony when they do not truly believe in the Sikh faith.

"No-one is telling you not to marry your son or daughter to whoever you like - but don't use our guru as an excuse to do it," he said.

There are around 300 gurdwaras in Britain and each is run by elected committees of worshippers.

The rules on the anand karaj, which is the formal name for the Sikh wedding, are set by the religion's governing body which is based at the Golden Temple in Amritsar, India.

In 2007 it advised gurdwaras the anand karaj should only be between two Sikhs and the protesters say some gurdwara committees are not respecting the faith by allowing non-Sikhs who do not believe in the religion to marry there.

Professor Gurharpal Singh, from the School of Oriental and African Studies, says the rise in mixed faith weddings has led to objections.

Prof Singh, an expert in the Sikh faith, said: "Previously mixed marriages were rare and they were - in a sense - tolerated. But now we are seeing a greater number of mixed marriages and correspondingly the reaction against those marriages from those who believe that the formal Sikh tradition says that only Sikhs should marry Sikhs."

The Sikh Council - an umbrella body for Sikh organisations in the UK - has condemned the violence and threats but agrees with the sentiment of the protesters.

The council's secretary general, Gurmel Singh, said: "I would say there is no place in a modern Britain for any community to resort to violent threatening behaviour."

Image caption A rise in mixed faith weddings has led to an increase in these protests

But Mr Singh said: "The person getting married has to accept the concept of one god and renounce any other beliefs they may hold which are contrary to that.

"They would also need to understand what the Sikh marriage entails. They would need to adopt (the surname) Singh or Kaur as they are what defines a Sikh. We don't have legal powers so it is not legally enforceable but it is a social contract a contract of commitment."

The protests have made many gurdwaras incredibly nervous about conducting mixed faith weddings and, while some said they were willing to hold ceremonies, they did not want to speak about the issue publicly.

Secret weddings

BBC Asian Network has learned of couples struggling to book weddings in some temples and of other couples getting married in secret, in front of a handful of guests.

One Sikh bride who got married to her Christian husband in secret in December sacrificed a traditional big Asian wedding for a tiny ceremony in front of a few relatives. She did not want to give her name for fear of reprisals.

"The night before the wedding we were wondering what to do if there was any trouble - it was really stressful and upsetting," she said.

Dr Piara Singh Bhogal has sat on the committee that runs the Ramgariha gurdwara in Birmingham and he said he shared the protesters' views on Sikh-only weddings but objects to the way protesters are ruining the most important day of a couple's life.

"This issue now is becoming quite serious because ceremonies have been disrupted. I am hearing about once a month, sometimes twice a month ceremonies are being disrupted. People are getting scared," he said.

You can hear the full documentary The Sikh Wedding Crashers on the BBC Asian Network on Monday 11 March at 17:00 GMT or listen back on BBC iPlayer.