A founder and former chairperson and General Secretary of the Sligo–Leitrim Independent Socialist Organisation he has been a lifelong political activist.

[2] An active trade unionist he is a former member of the Western branch Committee of the Federated Workers Union of Ireland.

The State military files released last year after 30 years which highlighted the whereabouts and activities of suspected 'subversives', included Bree as well as other prominent activists such as Tomás Mac Giolla, Cathal Goulding, James Kelly and Ruairí Ó Brádaigh.

Bree, in answer to this new notoriety, said 'This reflected the general paranoia of Church and State in the Ireland during the 60s and 70s, and "Practically everyone active in left wing politics at the time was considered dangerous and subversive," he added.

A 2009 report, commissioned after a walk-out by officials of Sligo Borough Council, found that remarks made at that meeting by him in relation to the proposed funding of a footbridge from a private development at Swan Point to Markievicz Road were "inappropriate and bullying".

[5] Bree was involved in negotiations to set up the United Left Alliance in November 2010; however, disagreements arose and he did not join then.