The arrest of Sinn Féin MLA Francie Brolly in connection with the Claudy bombing of 1972 will be raised by Sinn Féin when a party delegation meets Taoiseach Bertie Ahern in Dublin this afternoon.
The party is angry at Mr Brolly's arrest, claiming it to be a PSNI Special Branch smear campaign. Two other men and a women were also arrested on Tuesday over the attack.
Party general secretary Mitchel McLaughlin last night said the arrest was not a police attempt to bring those responsible to justice. "It was driven by a core of former RUC personnel still at the heart of the PSNI Special Branch."
At a press conference this morning, Mr Brolly denied any involvement in the attack and claimed the only reason given for him being treated as a suspect was that he lived 10 miles from the scene of the blast.
He said: "I'm really seething with anger. These people could have come to my house at any time if they wanted to see me about Claudy.
"The whole charade about the arrest reminded me of internment."
Mr Brolly added: "This has harmed me personally and it has harmed my family. Apart from the political kind of undertones, it has been a character assassination."
Mr Brolly was released last night along with the other three detained. A file is to be sent to the North's Public Prosecution Service.
Six adults and three children were killed when three IRA car bombs exploded in the Co Derry village without warning.
The Sinn Féin delegation meeting Mr Ahern will be led by party president Gerry Adams and will include chief negotiator Martin McGuinness, Dail leader Caoimhghín Ó Caoláin and Mary Lou McDonald MEP.
Sinn Féin's latest run-in with the police will not be helpful to Mr Ahern's attempts to convince the party to sign up to the North's policing bodies - a key aspect of former British Home secretary Chris Patten's recommendations on police reform.
Another matter of concern for Sinn Féin is the passing of files stolen from Castlereagh police station to unionist paramilitaries. The files contained details of hundreds of republicans and nationalists, including their homes addresses.
However, the Taoiseach's moves to resolve the on-the-runs (OTRs) issue despite Opposition pressure, has been well creceived by Sinn Féin who are pushing for the full retoration of Northern power-sharing now the IRA has declared an end to its armed campaign.
The controversy over Irish Ferries is also due to be raised today.