Irish premier Leo Varadkar has said Sinn Fein is not “guilty by association” with its former councillor Jonathan Dowdall, but the party should vote to renew Ireland’s non-jury court in June.

He also called on Sinn Fein to give more detail about its knowledge of the actions of Dowdall, who is in prison for his involvement in the 2016 Regency Hotel murder.

David Byrne, 33, died after being shot six times at a boxing weigh-in at the Dublin hotel on February 5 2016 in an attack that judges said sparked a series of “callous” gangland murders in the capital.

Gerry “The Monk” Hutch, 60, was found not guilty on Monday of Mr Byrne’s murder after evidence from the state’s key witness – Dowdall – was largely dismissed as unreliable without corroboration.

Gerry ‘The Monk’ Hutch outside the Special Criminal Court in Dublin on Monday (Sam Boal/PA)

The three-judge panel concluded that audio recordings of a conversation between Mr Hutch and Dowdall from March 2016 “does not provide independent evidence” to back up his allegations that Mr Hutch was one of the six people involved in the attack on the day.

Dowdall, who gave a statement to gardai 10 days before he was to stand trial for murder, is serving a four-year prison sentence after he pleaded guilty to a lesser charge of facilitating the murder of Mr Byrne through the booking of a hotel room used by one of the hit team.

Sinn Fein leader Mary Lou McDonald issued a statement after the Regency verdict to say Dowdall “should never have been a member of Sinn Fein” given what he “would become involved in”.

He had been a councillor on Dublin City Council in 2014, before leaving a short time later.

Mary Lou McDonald (Niall Carson/PA)

Speaking in the Dail on Tuesday, Mr Varadkar said: “I don’t think for a second that Sinn Fein is in any way responsible for Dowdall’s actions.

“I know it can be difficult to vet candidates and I don’t believe in guilt by association.”

But he added that many convictions would not have been possible without the non-jury Special Criminal Court, and called on Sinn Fein to emphatically support it.

“I do want to call on Sinn Fein, to call on the leaders of Sinn Fein in particular, to affirm that they will vote for the renewal of the Special Criminal Court in June – not an abstention, not not turning up – that you will vote for the retention of the Special Criminal Court.”

Tanaiste Micheal Martin told reporters in Belfast that the suggestion that Sinn Fein officials may have known about a 2011 gun attack on the home of Dowdall’s uncle – as suggested in evidence heard during the murder trial – undermined Ms McDonald’s claim that the party had no knowledge of Dowdall’s involvement in criminality.

Micheal Martin (Niall Carson/PA)

“It is very difficult to comprehend the lack of knowledge of what Jonathan Dowdall was up to at the time when he was elected Sinn Fein councillor in Dublin,” he said.

“Sinn Fein need to clarify that point.”

Asked for her response to claims that Sinn Fein knew about Dowdall’s links to criminality nine years ago, the party’s Stormont leader Michelle O’Neill said: “That’s absolutely not true. I think Mary Lou set the record straight on that.”

She said Ms McDonald delivered “very firm words” about the matter on Monday night.

“Of course, if we ever knew that someone of that character was joining our membership he would not have been allowed.”

On Monday, the Special Criminal Court found two men guilty of facilitating the murder of Mr Byrne through providing motor vehicles that contributed to a serious offence by a criminal organisation.

Leo Varadkar (Julien Behal Photography/PA)

Speaking in the Dail on Tuesday, Mr Varadkar agreed that the Special Criminal Court was essential to provide safer communities.

“The Regency murder trial is now over, we’ve two convictions of people who are involved in serious organised crime. I want to thank the Garda, the (Director of Public Prosecutions) and the courts for their work,” he said.

“We’ve had no murders related to a criminal gang feud in Ireland in five years now, please god that will continue.

“I think the fact that there was one acquittal, even though it was not the outcome that the state desired, does confirm that the Special Criminal Court is a place that people get a fair trial and the ‘beyond reasonable doubt’ principle applies.

“It does show that the Special Criminal Court works.

“The evidence does show a clear and ongoing link and overlap between Republican paramilitaries and organised criminal gangs. These are similar people who commit similar crimes. It was always thus, they are not worlds apart – in fact, they inhabit the same netherworld, in my view.”