Nigel Farage has refused to criticise Donald Trump’s claims that paracetamol, sold in the US as Tylenol, could cause autism, insisting “science is never settled” and he would never “side with” medical experts.

The Reform UK leader said he had “no idea” if the US president was right to tell pregnant women to avoid taking acetaminophen, also known as Tylenol and paracetamol, and suggesting that those who could not “tough it out” should limit their intake.

Scientists and global health agencies including the World Health Organization have strongly dismissed Trump’s false claims, calling them misguided and saying the evidence linking paracetamol use in pregnancy and autism was “inconsistent”.

The UK’s health secretary, Wes Streeting, told the British public they should not “pay any attention whatsoever to what Donald Trump says about medicine”, adding: “I trust doctors over President Trump frankly, on this.”

But in a wide-ranging interview with LBC’s Nick Ferrari, Farage was asked directly if Trump was right to share those unproven claims. He said: “I have no idea, I’ve no idea. You know we were told thalidomide was a very safe drug and it wasn’t. Who knows Nick, I don’t know.

“He [Trump] has a particular thing about autism. I think because there’s been some in his family, he feels it very personally. I’ve no idea.”

When Farage was asked if he would side with medical experts who say it is dangerous to make the link, he added: “I wouldn’t. I wouldn’t. When it comes to science, I don’t side with anybody, right? You know? I don’t side with anybody, because science is never settled. We should remember that.”

Yet when challenged over whether it was irresponsible for Trump to make such an unproven claim, Farage said: “That’s an opinion he’s [Trump’s] got. It’s not one that I necessarily share.”

Farage’s refusal to condemn Trump’s claims comes weeks after a controversial doctor, Aseem Malhotra, was given top billing at Reform UK’s party conference and used his main-stage speech to claim the Covid vaccine caused cancer in the royal family. Malhotra is an adviser to Trump’s health secretary, Robert F Kennedy.

In the same interview, Farage said Trump was “right to say” that sharia law “is an issue in London”.

“Never take what he [Trump] says literally, ever on anything. But always take everything he says seriously,” Farage said, adding: Trump “has a point.”

“So is he right to say that sharia is an issue in London? Yes. Is it an overwhelming issue at this stage? No. Has the mayor of London directly linked himself to it? No.”

Labour MPs have urged Keir Starmer to reprimand Trump’s administration after the US president falsely claimed in a speech to the United Nations: “I look at London, where you have a terrible mayor, terrible, terrible mayor, and it’s been changed, it’s been so changed.

“Now they want to go to sharia law. But you are in a different country, you can’t do that.”

Trump has been publicly attacking the London mayor, Sadiq Khan, since 2015 when the Labour politician criticised Trump, the then presidential candidate, for suggesting that Muslims should be banned from travelling to the US.

A spokesperson for Khan said: “We are not going to dignify his appalling and bigoted comments with a response. London is the greatest city in the world, safer than major US cities and we’re delighted to welcome the record number of US citizens moving here.”

During the LBC phone-in, Farage also said Reform’s plan to ban anyone who was not a UK citizen from claiming benefits would not apply to Ukrainians and Hongkongers.

“No, because they come for different reasons,” Farage said, adding those who had lived in the UK on indefinite leave to remain and had not worked or paid into the system would be told their benefits would be cut.