Boris Johnson was attacked by angry Sikh residents during a visit to a temple in Bristol, after telling them he would make it easier to trade alcohol between the UK and India.

Seemingly unaware that the drinking of alcohol is forbidden under many Sikh teachings, the Foreign Secretary told the 50-strong crowd that he was going to sign a free trade deal in order to boost the trade in whisky.

“I hope I’m not embarrassing anybody here by saying that whenever we go to India – Mumbai or to Delhi – we have to bring clinking in our luggage,” he said. “We have to bring Johnnie Walker, we have to bring whisky.”

“There is a duty of 150 per cent in India on imports of Scotch whisky. So we have to bring it in duty free for our relatives. But imagine what we could do if there was a trade deal with India, which there will be, because then the tariffs would go.”

His comments provoked a furious response from some members of the crowd, but one woman, Balbir Kaur, was described by witnesses as being “absolutely livid”.

“How dare you talk about alcohol in a Sikh temple,” she said.

“You are standing in a Sikh [temple] talking about alcohol which is absolutely outrageous – it’s absolutely not right.”

The former Mayor of London replied: “I’m very sorry if you think that alcohol is a bad thing – I understand your point of view. It is not, though, the view of every religion. There are plenty of Sikhs who are good and practising Sikhs who don’t take your attitude.

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“I do think it is relevant to our considerations that whisky is a huge business in this country and a free trade deal with India would be of great value.”

Ms Kaur then told Mr Johnson that she had relatives who had suffered from alcoholism.

Others members of the crowd reportedly told Mr Johnson that if he had made the comments in India, he “would not have got out of the temple alive”.

Some were also said to have quietly attempted to advise Mr Johnson to stop discussing alcohol when he began speaking about whisky. Their requests were reportedly ignored.

Following the gaffe, critics accused the Foreign Secretary, calling him an “insensitive blunderbuss”.

Stephen Pound, who is seeking re-election as Labour MP for Ealing North said: “Once he was a clown, now he’s a calamity: these crass remarks make plain why the Tories are desperate to keep Boris Johnson away from the cameras. He is an incompetent, insensitive blunderbuss and, as Foreign Secretary, an increasing liability.

“With every incident like this, we are reminded of Theresa May’s appalling judgement in appointing this man to one of the great offices of state.”

Tom Brake, the Liberal Democrats’ shadow Foreign Secretary, said: “This crass misjudgement has shown Boris Johnson is incapable of representing his own party at home, let alone representing Britain abroad.

“It doesn’t bode well for all the trade deals the Brexiteers have promised.”

A Conservative spokesperson said: “He was simply making the point that a free trade deal with, for example, India could be huge for both sides, pointing out that in India billions of litres of whisky are consumed every year but there is a 120 per cent [duty] on imports of Scotch whisky.

“Wouldn’t it be great if we could have free trade?

“One lady expressed her views based on a personal situation but the other 30 attendees warmly welcomed his remarks.”