A Canadian journalist has become the third so-called anti-Muslim activist accused of racism to be barred from Britain in just 72 hours.

Border guards quizzed Lauren Southern for six hours in Calais where she was preparing to come to the UK to interview English Defence League co-founder Tommy Robinson.

It is understood the 22-year-old was hauled in for questioning over concerns surrounding an incident last month in Luton where she is accused of distributing racist material in the form of Islamic posters.

On Friday, right-wing Austrian activist Martin Sellner and his American girlfriend Brittany Pettibone, a YouTube commentator and author, were detained by the British government.

Lauren Southern, 22, who is a Canadian journalist, was denied entry to Britain after she was detained in Calais

Border guards quizzed Lauren Southern (pictured) for six hours in Calais where she was preparing to come to the UK to interview English Defence League co-founder Tommy Robinson

Martin Sellner of the Generation Identity group and American commentator Brittany Pettibone say they were denied entry to Britain

Sellner said on the video that both of them were handcuffed. He said he planned to give a speech at Speakers' Corner in London's Hyde Park - 'that was my crime.'

Southern took to Twitter to document the incident, and said: 'I'm not kidding about this, but during my questioning by the UK police.

'I was asked about my Christianity and whether I'm a radical. I was also asked how I feel about running Muslims over with cars.

A British security official confirmed all three had been refused entry and said when Sellner and Pettibone landed at Luton Airport, north of London, on Friday, border police refused to allow them to enter Britain.

They were detained and then deported on Sunday.

The official, who spoke on the condition of anonymity, said the couple had been banned from entering by Britain's Home Office on the grounds that their 'presence in the UK was not conducive to the public good'.

On Monday, British border police stationed in the French port of Calais also denied entry to Southern.

After being detained, Southern tweeted that British authorities had told her she was 'officially banned from UK for "racism"'.

The official confirmed that British border authorities had denied Southern permission to enter Britain on the same grounds as the other two activists.

Southern was planning to meet Sellner and Pettibone in Britain, according to the conservative news website Breitbart.

Breitbart also said Sellner had been planning to make a speech in London's Hyde Park, but that papers served on him by the British authorities alleged the speech was likely to incite 'tensions between local communities'.

Breitbart said Pettibone was blocked from entering Britain not only in relation to Sellner's planned speech but also because she planned to interview Tommy Robinson.

Experts who monitor Britain's far right movements said the government had recently stepped up efforts to keep out ultra-right-wing foreign activists.

Among other Americans who have been banned from Britain are anti-Muslim campaigners Robert Spencer and Pamela Geller, and Mark Weber, who heads a California group known for Holocaust denial.

Sellner said in a video posted on Twitter they were detained for three days and then deported

Sellner of the Generation Identity group and American commentator Pettibone tweeted Monday that they were denied entry into Britain.

Sellner said in a video posted on Twitter they were detained for three days and then deported.

He said on the video that both of them were handcuffed. He said he planned to give a speech at Speakers' Corner in London's Hyde Park - 'that was my crime.'

Pettibone said that she was denied entry because she planned to interview far-right leader Tommy Robinson.

She said from Austria: 'It felt like they were saying,"you're right-wing, that's not allowed".'

Their entry was supposedly denied a day after his group claimed he and Pettibone were detained at the border and then turned away.

A supporter of Martin Sellner is pictured with a lighted flare that was thrown at the group at Speakers' Corner as the Austrian far-right activist said he would address a crowd, but now won't be able to

Demonstrators have taken to London's Hyde Park after far-right Austrian activist Martin Sellner said he was planning to speak there on Sunday

Pictures today showed demonstrators turning out on both sides as supporters of Mr Sellner clashed with anti-fascist protesters

A supporter of Martin Sellner holds a lighted flare that was thrown at protesters

Supporters of Martin Sellner and Brittany Pettibone at Speakers Corner were confronted by members of London Anifacists

The Home Office said the department would not comment on whether Mr Sellner or his girlfriend had been detained, the Evening Standard reported on Sunday.

Mr Sellner said that 'security risks' and 'left wing threats' forced him to cancel an earlier planned event with UKIP's youth wing Young Independence.

Pictures on Sunday showed demonstrators turning out on both sides as supporters of Mr Sellner clashed with anti-fascist protesters.

'This massive immigration is changing the face of our streets, of our cities, and soon the people who have been living here for thousands of years will be an endangered minority,' Sellner said last year.

Supporters of the Austrian activist held up placards saying 'Free Sellner' amid claims he and his girlfriend had been refused entry at the UK border

The demonstration broke out at Hyde Park after Mr Sellner said he would speak there following the cancellation of an event with UKIP's youth wing

A police officer stands next to signs supporting right-wing Austrian activist Martin Sellner

The Facebook page of Generation Identity claims that Martin Sellner (pictured in Vienna in 2015) was denied entry at the UK border

He tweeted last Tuesday: 'My speech for the Young Independence conference was cancelled for the 2nd time, due to security risks caused by left wing threats.

'But we won't be silenced. On Sunday the 11th I will give my speech on Speakers' Corner and I invite everybody who had a ticket for the conference to come!'

Hope Not Hate said Generation Identity had been handing out leaflets near Hyde Park before the planned speech.