Six Irish MEPs are supporting the Sunday Tribune Northern Editor's refusal to hand over phones, computers, notes and other material relating to stories on the Real IRA.
Fianna Fáil's Eoin Ryan and Brian Crowley, Labour's Proinsias de Rossa and Mairead McGuinness of Fine Gael have endorsed Suzanne Breen's refusal to disclose sources to the PSNI. Sinn Féin MEPs Mary Lou McDonald and Bairbre de Brun are also backing the Sunday Tribune and National Union of Journalists' (NUJ) campaign to protect sources. Fine Gael Dáil candidate George Lee and Green TD Ciaran Cuffe also offered strong endorsement.
A petition supporting Breen has attracted thousands of signatures from journalists, writers, artists, academics, victims of paramilitary and state violence, ex-police officers and civil-liberties campaigners across the globe.
Others endorsing the campaign include Euro candidates Ivana Bacik, Alex White, Nessa Childers and Susan O'Keefe of Labour, Joe Higgins of the Socialist Party as well as Senator David Norris.
O'Keefe said: "As someone who fought to the Circuit Criminal Court to protect my sources, I fully support Ms Breen's right to maintain the confidentiality of sources in her story. She described the PSNI's "heavy-handed reaction" as "a disturbing infringement of press freedom".
DUP justice spokesman Ian Paisley jnr, who recently faced legal action himself for not revealing sources to the Billy Wright murder inquiry, supports the Sunday Tribune.
He said: "Suzanne Breen has a reputation for being very diligent and upright. In all my dealings with her, I've found her journalistic approach to be professional and skilful. When she has put matters to me, she has never breached a confidence or revealed the source of her material. As a journalist, she must be able to protect her sources. I've no hesitation in offering my support."
Breen will address an NUJ rally in London on Tuesday. Sunday Tribune Editor Nóirín Hegarty will launch a campaign for sources' protection in Dublin on Thursday. The case, which was due to open in Belfast on Friday, is expected to be heard next month.