Costello was first elected as a TD in 1992. He kept his seat until the 2016 general election. He was elected as a Senator in 1989 on the administrative panel. He is the Labour spokesperson for urban regeneration. He was elected to Dublin City Council in 2019. He is a former Minister of State and spokesperson on issues including education, justice and transport. He is a former secondary school teacher.

I have worked hard for my constituents over the years and through my weekly advice centres, I have considerable knowledge of the issues facing people in Dublin Central.

Housing and homelessness are the biggest issues in my constituency. 80% of the people who come to my weekly advice centre have issues related to rent, notices to quit, overcrowding, homelessness and inability to purchase their own homes.

My number one priority for the first hundred days in the new Dáil would be to establish a national housing authority to address the crisis of housing and homelessness, and give it the powers and resources to plan and deliver public housing throughout the country.