"At Queen's Birthday party, presented with picture of The Queen at Golden Mosque in Amritsar in 1997, a permanent memento for Deputy High Commission's wall," he tweeted.
On realising his mistake, he apologised for the gaffe.
"I was wrong: I am sorry. I should of course have said the Golden Temple or, better, Sri Harmandir Sahib," the British Foreign Office top diplomat said today morning.
However, Bhai Amrik Singh, the chairman of the Sikh Federation, said it was a "major gaffe" by a top civil servant and "totally unacceptable". "It demonstrates a remarkable level of ignorance from someone in his position," Mr Singh said.
"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," Mr Singh was quoted as saying by The Guardian.
Simon McDonald's error follows criticism of Foreign Secretary Boris Johnson for risking offending Buddhists during a 2017 visit to the Shwedagon Pagoda, a sacred site in Myanmar's capital, Yangon.
Andrew Patrick, the UK's ambassador to Myanmar, was forced to tell Mr Johnson to stop reciting the opening verse to Rudyard Kipling's "The Road to Mandalay", which chronicles a retired British serviceman's memories of colonial service. "Not appropriate," he was caught on camera telling Britain's top diplomat.
With inputs from PTI and AFP