A major reshuffle of Prime Minister Julia Gillard's cabinet is expected following news two of her ministers will step down today. 

Chris Evans will announce his retirement as government leader in the Senate and minister for tertiary education, skills, science and research.

Attorney-General Nicola Roxon is also expected to resign from cabinet today.

News Limited says Ms Roxon will remain in parliament and quit politics at the September 14 election.

It's tipped Parliamentary Secretary for Climate Change Mark Dreyfus QC, a former Melbourne barrister, will replace Ms Roxon.

In the Senate, both Stephen Conroy and Kim Carr are reported to be keen to take over as government leader.