He was called to the Melbourne bar in 1872 and was also active in public life, being a noted campaigner for divorce law reform.

As a result, when Munro suddenly resigned in the face of imminent bankruptcy in February 1892, the liberals turned to Shiels as a "clean" new leader, and he became Premier.

The Shiels government responded to the financial disaster of the 1892 crash in the orthodox fashion of the time, cutting spending and increasing taxation to balance the budget – measures which only made the situation worse.

The conservatives who had supported the coalition governments of Duncan Gillies and Munro opposed increased taxation, and during 1892 they deserted Shiels.

In January 1893 the conservative leader James Patterson moved a successful no-confidence motion, and Shiels resigned.