Mr Shorten issued a short statement on Monday to say he would be taking some leave, and thanked his colleagues for their support.

"Yesterday, my mother Ann passed away," he said. "I was very close to my mum - and her passing has come as a shock to me and my family."

Ann Shorten was 79.

Mr Shorten said he still hoped to deliver the speech in which he was expected to urge the scrapping of a requirement for union membership for Labor Party members.

“Today I was scheduled to speak in Melbourne about modernising the Australian Labor Party,” he said.

“I hope to deliver that speech in the near future.”

Senator Penny Wong will be Labor’s acting leader while Mr Shorten takes leave and deputy leader Tanya Plibersek is overseas.

“My family and I have received many kind messages of support from friends, colleagues and members of the community for which we are very grateful,” Mr Shorten said.

“On behalf of Chloe and our children, my brother Rob and his family, I thank you for respecting our privacy while we grieve.”

Ann Shorten went back to work as a teacher to help pay the fees to put Mr Shorten and his twin brother Rob through school at Melbourne's Xavier College.

In an interview with News Corp last year, Mr Shorten said his mother was a big influence on who he was and the value of education.

"She's taught me that teaching shouldn't be denigrated; that we ask a lot of teachers and they give a lot back."