Victorian MP Catherine Cumming, who came under fire for hiring her own children and friends, has been revealed as the parliament's biggest spender on discretionary salaries.

Ms Cumming spent an extra $43,010 on staff salaries in the last three months of 2019 – in addition to the money she was allocated to employ staff in her office.

Catherine Cumming in 2012, when she was elected mayor of Maribyrnong. Credit:Martina Gemmola

The upper house MP was elected on Derryn Hinch's Justice Party ticket, winning 6.77 per cent of the vote in her Western Metropolitan electorate, but spectacularly quit his party the day before she was due to be sworn in.

Ms Cumming said because she was originally elected as a member of a political party, she was entitled to employ the equivalent of 2.5 full-time staff members – unlike other independents who are entitled to employ the equivalent of 3.5 full-time staffers.