A Conservative council candidate in Watford, Darren Harrison, has been suspended after it was alleged that he was a supporter of the pan-European white supremacist organisation Generation Identity and associated with the English Defence League’s former leader Tommy Robinson.

A statement issued on Friday by Conservative central office in London said: “Darren Harrison has been suspended. An investigation is under way.”

Harrison was contesting the Tudor ward in the Liberal Democrat-run borough, which is currently made up of 26 Lib Dem and 11 Labour councillors. He had campaigned with James Cleverly, a Tory party vice-chairman, and featured on local party social media. Harrison’s Twitter account is no longer accessible and there is no mention of him on the local party’s website.

His links with Generation Identity, an anti-Islam organisation with strong links to far-right groups across Europe, were alleged in an investigation by Vice News.

Harrison denied being a supporter of Generation Identity, saying: “I do not support their views, but support their right to have their views, as I do anyone else, as long as it does not promote violence which to my knowledge, it does not.”

One of GI’s leaders Martin Sellner, an Austrian, and his girlfriend, Brittany Pettibone, an American alt-right commentator, have been banned from entering the UK.

Sellner was stopped at Stansted airport at the weekend when he planned to address the movement’s first conference in Sevenoaks, Kent. The event broke up early and some attendees were confronted by anti-fascist campaigners. Scuffles broke out and one protester was arrested.

GI’s social media feed is full of racist slurs and highlights court cases involving refugees and migrants.

The suspension of Harrison comes at the end of a difficult week for the government. It has been dominated by its disastrous handling of the long-settled Windrush generation and the way the Home Office’s hostile environment has operated. Renewed evidence of racist and extremist links will compound the impression of a party that is not good enough at policing its members’ affiliations.

In the London mayoral elections in 2016, the Tory candidate Zac Goldsmith’s campaign against Sadiq Khan was widely condemned for its anti-Muslim overtones.

The party appeared to be struggling to recruit candidates for the local elections on 3 May, although sources now say it has candidates for all but a handful of the 4,413 seats being contested.