The Foreign Office's top official has apologised after calling one of the most revered Sikh temples a mosque.
Sir Simon McDonald said "I was wrong" after inadvertently referring to the Golden Temple in Amritsar, India, as the "Golden Mosque".
His blunder came as Labour leader Jeremy Corbyn promised he would launch an independent inquiry into Britain's military role in the Indian army's 1984 raid on the Golden Temple if he became prime minister.
Sir Simon's embarrassing gaffe was made on Twitter, where the Foreign Office permanent secretary referred to a picture of the "Golden Mosque" being presented to the UK's deputy high commissioner.
After realising the error, he said: "I was wrong: I am sorry. I should of course have said the Golden Temple or, better, Sri Harmandir Sahib."
Bhai Amrik Singh, chairman of the Sikh Federation, said: "This was a major gaffe by a top civil servant and totally unacceptable.
"It demonstrates a remarkable level of ignorance from someone in his position."
He added: "In our view, a public apology and admitting the mistake is not enough.
"What we need is a commitment from the UK Government and senior civil servants to root out such ignorance and discrimination or we will continue to face hate, abuse and threats of violence."
The mistake is particularly sensitive given the suspicions about the extent of UK involvement in the 1984 raid.
Labour leader Mr Corbyn's pledge to carry out a probe into the assault, which is said to have left thousands of people dead, will be included in the party's next manifesto.
Speaking at a Sikh Federation event in Watford, Mr Corbyn said: "You can be very sure that, whenever the election comes, it will be in the next manifesto ... it's a commitment that's going to be there and we will honour that commitment."
A 2014 investigation by David Cameron's Cabinet secretary, Sir Jeremy Heywood, said a British officer's advice to Indian authorities about how to resolve a stand-off with Sikh dissidents was ignored by army chiefs who ordered the offensive.
Mr Cameron said there was "absolutely no evidence" of UK government involvement in the raid on the Golden Temple complex.
The finding was met with "disappointment" by British Sikh groups and the Sikh Federation said Sir Jeremy's review was "limited in scope".