Liberal MP Michael Keenan has become the latest minister to quit Scott Morrison’s government, in another major blow before the election.

The Human Services and Digital Transformation Minister’s announcement follows the resignation of Industrial Relations Minister Kelly O’Dwyer less than a week ago.

“I have been an absent father in the lives of my children and now is the time for this to stop. With a newborn child — our family’s fourth — it is unworkable for my family,” Mr Keenan said in a statement on Friday.

Mr Keenan, who has been in politics for 15 years, said the decision became clear to him during the Christmas break.

The member for Stirling in Perth, Western Australia, described politics as a “proud vocation” but one that was difficult and exhausting. He insisted he remained “resolutely optimistic” about the coalition’s prospects at the upcoming federal election.

“The government’s plan for a stronger economy is working. This is why I believe the coalition can and will win the next election,” he said.

Finance Minister Mathias Cormann said Mr Keenan had made an “outstanding contribution” to his community and to federal parliament.

“We are sad to see him go, but entirely understand and respect the reasons for his decision,” Senator Cormann said in a statement on Friday.

Mr Keenan has previously held the justice and counter-terrorism portfolios. His retirement is the second recent loss for the Morrison government after Ms O’Dwyer said she wouldn’t recontest the seat of Higgins in Melbourne to spend more time with her family and to try for a third child.

The election is expected in May this year.