Dean Nalder has reportedly become the second WA minister to quit the cabinet in a rebellion against Premier Colin Barnett.
Mr Nalder, the transport minister, told The Sunday Times in Perth he was frustrated at the premier's "erratic and illogical" decisions.
He is the second minister to quit on Saturday after Tony Simpson stepped down earlier in the day.
"Colin is making irrational decisions without consultation with respect to ministers or cabinet," Mr Nalder told the newspaper on Saturday night.
The announcement has increased pressure on Mr Barnett's leadership less than six months before the WA state election on March 11.
Mr Nalder, who is considered a leadership aspirant, was told by the premier to take a week off late last month following a damning private poll funded by wealthy businessmen that indicated Barnett's Liberal National government would lose the election.
Earlier in the day Mr Simpson said he no longer supported the premier and the state government had lost its way.
Mr Simpson has been a cabinet member and the minister for local government, community services, seniors and volunteering and youth since 2013.
He said he wanted the Liberal leadership issue to come to a head and sharply criticised Mr Barnett, who was elected premier eight years ago this month.
"I don't think, honestly, I can sit in cabinet anymore and be part of a government making decisions when I don't believe it's going in the right direction," he told reporters on Saturday.
"Our government has won two elections on good policy and good leadership ... Now it's actually lost its way."
The decision to quit was made with a heavy heart, but it was necessary, Mr Simpson said.
"Unless we make changes now, winning a third election seems very unlikely," he said.
The damning criticism comes on the same day a ReachTel poll of 1724 people was published in The West Australian newspaper putting Labor ahead 51-49 on a two party preferred basis, which is closer than previous polls.
Labor leader Mark McGowan was ahead of Mr Barnett as preferred premier 55-45.
Mr Barnett released a statement that did not acknowledge the criticism.
He thanked Mr Simpson for his service and said he had been a good minister and is a good local member.
"While I am sorry to see Tony leave cabinet, it now presents an opportunity for someone else to become a minister," he said.
