Members of the Sri Guru Singh Sabha Gurdwara in Southall, south-west London, said the final preparations were underway on Friday when the "thugs" came in, forcing the couple to call off their wedding plans.
"They were all thugs. None of them were recognised by any of the Sikh groups here. It was because it was a mixed marriage... They just came here to spoil it and intimidate us," gurdwara vice-president Sohan Singh Sumra told 'The Independent' newspaper.
"It was a sad day... We are living in this country and we work with couples - if they are happy we're fine with it - Sikhism is a liberal religion," he said.
Scotland Yard officers were called in to remove the "threatening" men and the gurdwara is now considering hiring private security.
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The men had reportedly also threatened to prevent the Sikh wedding ceremony from taking place in a phone call the night before but the bride's family had decided to go ahead.
The Sri Guru Singh Sabha Gurdwara is one of London's largest Sikh temples and was inaugurated by Prince Charles over a decade ago.
It led a meeting of other local gurdwaras on Saturday to try and look into ways of averting similar incidents in the future.
In October last year, the UK's Sikh Council had released "guidelines" on inter-faith marriages, which called on gurdwaras to ensure a "genuine acceptance of Sikh faith" in both partners, proposing the use of signed declarations.
The guidelines were developed through a consultation over a two-year period to define a "consistent" approach towards inter-faith marriages.