In an interview with ITV's Good Morning Britain, Donald Trump said he had known nothing about the organisation when he made the social media postings.

He told presenter Piers Morgan: "I knew nothing about them and I know nothing about them today other than I read a little bit.

"Perhaps it was a big story in Britain, perhaps it was a big story in the UK, but in the United States it wasn't a big story.

"If you are telling me they're horrible people, horrible racist people, I would certainly apologise if you'd like me to do that."

He said he had made the retweets because he was concerned about the threat posed by radical Islamic extremists.

Mr Trump said: "Look, it was done because I am a big believer in fighting radical Islamic terror. This was a depiction of radical Islamic terror.

"I don’t know who they are, I know nothing about them, so I wouldn’t be doing that. I am, as I say often, the least racist person that anybody’s going to meet. Certainly I wasn’t endorsing anybody. I knew nothing about them.

"They had I guess a couple of depictions of radical Islamic terror. Radical Islamic terror, whether you like talking about it or not Piers, it’s a fact.

"You look at what’s going on in UK and you look at what’s going on all over the world, you can try and shield it…”

Speaking afer the interview, presenter Piers described it as a "significant climbdown" from the American leader. 

He said: “I think it is significant. A lot of the antagonism I think from people in Britain towards Donald Trump was dramatically fuelled by retweeting one of the leaders of Britain First.

“Donald Trump made it clear to me that when he did these retweets he had no idea who this person was, he had no idea who Britain First was. He just thought that the videos, which to him depicted ISIS-like behaviour deserved a retweeted. I questioned him on that.

 “I think it was right and proper that he, now he was made aware - and I made him very clearly aware that these are racist, fascist people - that he should apologise and he said look, if they are these people you tell me they are then I would certainly apologise. I think that is a significant climb down by the President.”

Mr Trump caused outrage in Britain when he posted the three tweets last November, prompting Prime Minister Theresa May to say he was "wrong" to have done so.

The president subsequently pulled out of an expected visit to Britain to open the new US embassy building in London, leading to speculation of a diplomatic rift.

However, after meeting Mrs May at the World Economic Forum in Davos, Switzerland, on Thursday, he insisted that relations were in good shape.

He told Good Morning Britain: "I can tell you I have a very good relationship with your Prime Minister who I just left.

"She’s been doing a very good job. We actually have a very good relationship, although a lot of people think we don’t.

"I support her, I support a lot of what she does and a lot of what she says and I support you militarily very much.

"We will come to your defence if anything should happen, which hopefully will never happen. I am a tremendous supporter of the UK.”

Following the meeting, officials said Mr Trump would be making his first visit to the UK as US president later this year.

It appears likely, however, that the trip will not be the full state occasion to which Mr Trump was invited by Mrs May, but a lower-key working visit.

Mr Trump's appearance in the UK is not expected until the second half of 2018 - and is likely to be met by protests.

He said: “I hadn’t heard about banning, I think a lot of the people in your country like what I stand for, they respect what I stand for and I do stand for tough borders.”

Of those who don’t support his views he said: “I don’t care. I don’t care. It’s just one of those things, I don’t say anything. You know why? I don’t care.”

Downing Street said: "The PM and president concluded by asking officials to work together on finalising the details of a visit by the president to the UK later this year."

During their 40-minute meeting in Davos, Mrs May also raised the issue of aircraft manufacturer Bombardier, which has a major plant in Northern Ireland and is at the centre of a US trade dispute.

President Trump - The Piers Morgan Interview will air on Sunday at 10pm on ITV produced by ITV Studios Daytime