Nigel Farage was investigated by police after vowing to “take the knife to the pen pushers in Whitehall” after the UK leaves the EU.

The Brexit Party leader made the comments to around 500 supporters last week after criticising no-deal warnings from civil servants at a rally in Newport, South Wales.

It prompted a complaint from Naomi Long, a Northern Ireland MEP, that his remarks were “a clear case of incitement to violence against staff in the Civil Service”.

Gwent Police launched an investigation on Saturday before announcing a few hours later they had decided not to take any further action.

“We are aware of the heightened tensions that exist regarding use of language, and take all allegations and concerns from members of the public very seriously,” said Assistant Chief Constable Rhiannon Kirk.

“However, following a thorough assessment, it is our view that the comments in the video do not constitute a criminal offence.”

Farage launches his new Brexit Party: in pictures Show all 10 1 /10 Farage launches his new Brexit Party: in pictures Farage launches his new Brexit Party: in pictures Nigel Farage speaks at the launch of his new Brexit Party's campaign for the European elections Reuters Farage launches his new Brexit Party: in pictures Brexit Party candidate Annunziata Rees-Mogg, sister of Conservative MP Jacob Rees-Mogg, speaks at the launch AFP/Getty Farage launches his new Brexit Party: in pictures A supporter waits for Farage to speak AFP/Getty Farage launches his new Brexit Party: in pictures Supporters wait for Farage to speak AFP/Getty Farage launches his new Brexit Party: in pictures Farage's socks Reuters Farage launches his new Brexit Party: in pictures Farage and prospective candidate Annunziata Rees-Mogg wait at the launch AFP/Getty Farage launches his new Brexit Party: in pictures Supporters listen as Farage speaks AFP/Getty Farage launches his new Brexit Party: in pictures Free T-shirts for all attendees AFP/Getty Farage launches his new Brexit Party: in pictures Posters on the seats for supporters of the Brexit Party AFP/Getty Farage launches his new Brexit Party: in pictures A safety sign is pictured AFP/Getty

It comes after Boris Johnson was criticised for his “inflammatory” language in parliament when he referred to a law banning a no-deal Brexit as “the Surrender Act”.

The prime minister went on to dismiss MP’s fears about death threats by saying that the best way to honour murdered Jo Cox was to “deliver Brexit”.

Mr Farage’s speech, made at The Neon in Newport on 21 September, ended by focusing on the “wall of propaganda” about the dangers of a no-deal Brexit.

After mocking predictions of shortages of food and medicines contained in the Operation Yellowhammer documents, Mr Farage pointed to statements by the ports of Dover and Calais that they were “ready for Brexit”.

He added: “I suggest we listen to them and not the overpaid pen pushers in Whitehall who are not doing a neutral job, and once Brexit’s done, we will take the knife to them.”

As the crowd responded with loud cheers he said: “I’ve had enough of it. Had enough of all of it.”

After police announced they were looking into the allegations of incitement, Mr Farage partially retracted his comments by tweeting: “I should have said ‘take the axe’, which is a more traditional term for cuts.”

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Three months ago he demanded police take action against Jo Brand after the comic joked about throwing battery acid at politicians.