Sajid Javid has called for action to stop the UK “sliding into nationalism” as far-right movements grow in power around the world.

The home secretary appealed for a “national conversation about extremism” as he announced the government was drawing up a new strategy to combat multiple threats.

“Around the world, populism, prejudice – and even open racism – have catapulted extremists into power,” Mr Javid said.

“Thankfully our politics has not gone down the same road as much of Europe and the US, but we must act now, to avoid sliding into the barely masked racism of nationalism.”

Mr Javid praised Nigel Farage for leaving Ukip when Tommy Robinson was appointed as an adviser, saying the party’s support has “collapsed” because of its lurch to the right.

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He urged people not to label the Brexit Party extremists or “demonise anyone with a different view”, amid mounting polarisation in political debate.

Mr Javid delivered his speech at an event in London organised by the Commission for Countering Extremism, which published research on Friday finding that far-right protests in Britain are attracting the largest numbers since the 1930s.

The home secretary, who is expected to retain a cabinet post under the next prime minister, stopped short of labelling Donald Trump a racist but heavily criticised the US president’s calls for ethnic-minority American congresswomen to “go back” to other countries.

“I am deeply concerned about the polarisation we’re seeing in parts of the US, some of the naked populism we see and chants of ‘send her back’,” Mr Javid said, pledging that the UK would be a “critical friend” to American allies.

Mr Javid called on all public figures to “moderate their language” but refused to criticise Boris Johnson when The Independent highlighted his comments comparing Muslim women to letter boxes and bank robbers.

“It’s incumbent on all politicians to be careful about the language they use,” the home secretary said, before reiterating his support for Mr Johnson in the Conservative leadership race.

“He is someone who is passionately anti-extremist and passionately anti-racist, and embraces modern Britain,” he added.

Mr Javid insisted that the Conservative Party would root out anti-Muslim hatred in its own ranks and defended the government’s decision not to adopt a proposed definition of Islamophobia.

He accused the Labour Party of failing to address antisemitism and claimed that Jeremy Corbyn’s office had threatened to sue him amid a Twitter furore over a post from one of Mr Corbyn’s supporters.

The Independent understands that Mr Javid was sent a legal letter and issued a clarification, after which no further action was taken by Labour.

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The home secretary said the government’s 2015 counter-extremism strategy had focused on Islamists, and it was “time to take stock and talk openly about the threat and admit it’s got worse”.

“The faultlines dividing our society have splintered and spread,” he said, saying far-right extremism, antisemitism, Islamophobia and religious intolerance were all on the rise.

“We all have a role to play to stop the normalisation and legitimisation of these views.”

Mr Javid said he had barred several extremists, including the leader of white nationalist group Generation Identity, from entering the UK and would continue stripping British citizenship from dual-national Isis members in Syria.

He said the controversial campaign group Cage, whose research director described Jihadi John as a “beautiful young man”, would be stripped of its right to sponsor migrant workers.

Outlining a series of proposals to improve integration, Mr Javid said he would request more money for English-language lessons.

“We must not be afraid to confront these issues and be open and honest in public debate,” he added.

The government is to consider full recommendations from the Commission for Countering Extremism in September, following nationwide research on people’s views and experiences.

A survey found more than half of respondents had witnessed extremism online or in person.

Sara Khan, the lead commissioner, said people must retain the “right to be radical” and offensive.