Australia’s definition of marriage should respect, value and include every person, says Bill Shorten.

The federal Labor leader on Monday moved a private member’s bill to allow same-sex marriage, replacing “man and woman” with the words “two people” in the Marriage Act.

“Our laws should be a mirror reflecting our great and generous country and our free, inclusive society,” Shorten told parliament.

“And our parliament should be a place where we make things happen, rather than sit back and let them happen.”

Gay couples who have already married overseas will have their unions recognised under his bill.

Ministers of religion and other authorised celebrants will not be required to solemnise a marriage in which the parties to the marriage are of the same sex.

The full definition of marriage will be “the union of two people to the exclusion of all others, voluntarily entered into for life”.

Shorten said Coalition and Labor governments over past decades had delivered progress, from the Fraser government’s decriminalisation of homosexuality to the Rudd and Gillard governments amendment of 80 laws to remove discrimination.

There was nothing contradictory about having faith in God and supporting marriage equality, as it was an act of “extending love, compassion and charity”, he added.

Labor deputy leader Tanya Plibersek seconded the bill on Monday.

Only four Coalition MPs – Bob Baldwin, Darren Chester, Mal Brough and Andrew Broad – plus Speaker Bronwyn Bishop were in the chamber for the speech.

Chester and Brough were the only ones who did not have immediate parliamentary business in the chamber to attend to.

Forty-one out of 55 Labor lower house members were in the chamber.

Prime Minister Tony Abbott is yet to decide whether his frontbenchers will get a free vote, which they were denied in 2012 when Labor last brought on a private member’s bill.

Abbott said his priority was getting the budget through parliament.

“I accept that same-sex marriage is a significant issue,” Abbott told reporters in Canberra.

“But frankly, this government’s absolute fundamental priority … is the small business budget boost.”

He declined to say whether he thought there was majority community support.

“There’s a range of views on both sides of the issue and it’s an issue upon which decent people can disagree.”

Liberal MP Warren Entsch is seen as the most likely co-sponsor of a bipartisan bill, which may or may not take the same form as Labor’s.

Entsch met Abbott last week and was asked to come back with a proposal that could be taken forward in August once budget legislation was passed.

The Greens also want to be part of discussions, having already proposed their own bill.

– AAP