As Sinn Fein president Gerry Adams undergoes a fourth day of questioning by police, his colleague Martin McGuinness addressed a rally where he accused the “dark side” of the police service as responsible for Mr. Adam’s arrest.

Adams was arrested by the Police Service for Northern Ireland (PSNI) in connection with the 1972 murder of Jean McConville on April 30th.

Mrs McConville, a 37-year-old widow and mother of 10, was abducted from her flat in the Divis area of west Belfast and shot by the IRA.

Adams is being questioned for up to 17 hours a day by detectives, a source close to him told the BBC.

On Friday, a left-wing candidate for the European Commission Presidency, Alexis Tsipras, claimed Adams is a “scapegoat”, and said the Greek socialist also believes that Adams is a “pioneer of peace” and that his arrest is an “inflammatory act”.

The Belfast Telegraph reports the words of former terrorist and now deputy first minister of Northern Ireland Martin McGuinness, “There is a small cabal in the PSNI who have a different agenda. A negative and destructive agenda toward the peace process and to Sinn Fein. We under the leadership of Gerry Adams will not allow these elements to succeed. 

“Gerry Adams is my friend. Gerry Adams is the leader of Sinn Fein. And in my opinion Gerry Adams stands hand and shoulders above all of those who helped build this peace process”.

Speaking on Friday Sinn Fein assembly member Alex Maskey suggested his party would “review” its support for policing following the arrest of Mr. Adams, a comment that some have interpreted as a veiled threat.

“What we will continue to monitor and review is our relationship with the PSNI if indeed we have a situation which we believe is continuing at the moment, where we have a small element of people involved in policing who are politically motivated, who have a hostile attitude to our party, who have been taking very retrograde steps in relation to how they deal with policing.”

He told BBC Radio 4’s Today programme: “Police in any part of the world have to earn the respect of their local community. I can tell you that the community that I represent, the people that I represent are scathing in their anger at the moment about the PSNI.”

Conservative Party candidate Ben Howlett has also come under fire after he claimed that he “admired” Gerry Adams.