The Prime Minister has moved to capitalise on Opposition Leader Bill Shorten's appearance before the royal commission into union corruption, claiming the Labor Party is in crisis over the hearings.

The Coalition Government set up the royal commission, acting on an election promise to probe the governance of the unions and corruption claims.

Mr Shorten has been called to give evidence about his time as the Victorian and federal boss of the Australian Workers Union (AWU) and has moved to fast-track his appearance, which is now set for July 8.

Barrie Cassidy will interview Bill Shorten on Insiders at 9:00am (AEST) on ABC and ABC News 24

On Saturday he confirmed to the ABC that his ex-wife Deborah Beale had also been approached by the royal commission.

Fairfax reported Ms Beale was asked about some of her share dealings when she was married to Mr Shorten.

The ABC understands the commission has not asked her for any documents and she has not been called as a witness.

Labor MPs maintained the inquiry was a politically motivated attempt to tear down the Opposition Leader.

"This is a very, very expensive witch hunt. It's not about improving the safety of workers in particular industries," Labor frontbencher Matt Thistlethwaite told Sky News.

"It's not about improving the efficacy of the way our workplace relations system works.

"It's all about trying to damage the reputation of Bill Shorten."

But the Prime Minister used an address to the New South Wales Liberal conference in Sydney to accuse union leaders of failing to work in the interests of their members.

"We know the focus has been on a particular union and on a particular union leader over the last week or so," he said.

"But this is a crisis for the Labor Party more generally and what it shows is, as far as modern Labor is concerned, it isn't any more about the workers and their rights, it's about the union bosses and their privileges.

"What could be more shameful, what could be more embarrassing for someone who has a sacred trust to represent the workers of Australia, than to put himself or herself ahead of the interest whose job it is for them to represent, and yet that's what's happened."

Mr Shorten has declined to respond to specific questions that have been raised about payments companies made to the AWU while he was its state and federal leader.

The Opposition Leader's office said Mr Shorten would not be responding to matters that might be considered by the royal commission until he was able to appear before the inquiry.

A spokesman for the royal commission said all of the commission's inquiries "relate to matters within its terms of reference".

Liberal conference told to avoid factional 'poison'

The Prime Minister also used the Liberal conference to push for changes to make the party more inclusive and attractive to new members ahead of the next federal election.

As Liberal Party members cheered from the audience, Mr Abbott called for the party to be restored to its membership rather than being at the whim of factional influences.

"But let it be what I think and you think," he said.

"Let it not be what some faction boss tells us to think."

He said the party membership would grow if potential members knew they would "have a say" rather than just being invited to donate money and promote party candidates.

Former Liberal prime minister John Howard backed the comments and warned the party against becoming exclusive and narrow.

"Any mood or attitude inside the party that resists people coming in because they may upset some kind of factional balance is absolutely poison to the future strength and decency of our party," he said.