Britain First, estimated to have a membership of just around 1,000, said it had received hundreds of membership applications in the 24 hours after the US President was seen to endorse three of its videos on Twitter.
British Prime Minister Theresa May had described the group as a "hateful organisation that seeks to spread division" and said that Trump was "wrong" to have re-tweeted their messages.
The Facebook page of the organisation, a far-right group founded by former members of the far-right British National Party (BNP), has also been gaining supporters at a rate of more than one per minute since the US President's re-tweets earlier this week.
The group's deputy leader Jayda Fransen had earlier claimed that the sharing of her tweets by Trump amounted to an endorsement and pleaded with the US President to intervene in her forthcoming court case over using threatening and abusive language during an anti-Muslim speech at a rally in Belfast in August.
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The videos in question allegedly show an attack on a Dutch boy on crutches by a "Muslim migrant".
The other two, from 2013, showed a Syrian sheikh destroying a statue of the Virgin Mary and a man said to be linked to the Muslim Brotherhood throwing someone from a roof in Egypt.
During an urgent House of Commons debate yesterday over the row, British MPs called the US President fascist and stupid, accused him of "spreading evil" and said that he was "racist, incompetent or unthinking or all three".
They demanded that the British Prime Minister cancel a proposed state visit.
The trip, a scaled down version of a full-fledged state visit with no meeting with Queen Elizabeth II, was intended to allow Trump to come to the UK while avoiding mass protests.
But those plans have now been thrown off-track with the escalating Twitter row.