She is a former local branch officer with the Irish Nurses and Midwives Organisation, on the executive board of which she served in 1994.

[2] She first contested an election to Dáil Éireann in June 2001, when she stood on behalf of the WUAG in the Tipperary South by-election that followed the death of Theresa Ahearn; she polled 7,897 first preference votes.

She caused some controversy within the local Labour Party branch when she tried to nominate a family member to replace her on the council.

As a Member of the European Parliament, Prendergast spoke 127 times in plenary session and worked on the amendation of 32 reports.

[7] She was involved in a controversy with the Labour Party leadership when she became the first member of the parliamentary party to call for the resignation of Health Minister James Reilly, following the announcement of the location of primary care health centres in the minister's own constituency.