He was a member of the New South Wales Legislative Assembly representing Liverpool for the Labor Party from 1995 until 2023.

[2] Lynch originally ran for Labor Party preselection for Liverpool in 1989, but was defeated by Peter Anderson.

In the Keneally ministry, Lynch retained the Aboriginal Affairs portfolio, and took on responsibility for Industrial Relations, Commerce, Energy, and Public Sector Reform.

After the 2015 New South Wales state election, Lynch retained his position as Shadow Attorney General but was succeeded as Shadow Minister for Justice by Jodi McKay.

He retired at the 2023 New South Wales state election less than two years later.