The Maritime Union of Australia wants Labor leader Bill Shorten to reconsider the party's move to disendorse Chris Brown for the seat of Fremantle.

Key points: The MUA says the Labor Party should be "ashamed" over how it treated Chris Brown

The MUA says the Labor Party should be "ashamed" over how it treated Chris Brown The party says he should have disclosed his past convictions

The party says he should have disclosed his past convictions Josh Wilson is endorsed as the new ALP candidate

The ALP's national executive has selected Josh Wilson as its candidate for the seat after disendorsing Mr Brown over claims he failed to advise the party of convictions from the 1980s, including the assault of a police officer.

Mr Brown said claims he assaulted the police officer were wrong.

MUA national president Christy Cain said Mr Brown was the victim of the assault and disendorsing him was a disgusting attack on his character.

"We're calling on Bill Shorten, and the National Executive, to review the true facts, the legal facts, and then once they've seen that lets get on with the business which is getting the ALP elected," he said.

Mr Brown told reporters on Thursday he had never been convicted of the incident.

"The incidents from when I was a teenager have been expunged from my record," he said.

"Throughout our entire campaign I've been honest and truthful with the Labor Party on paper and in person.

"Fremantle has always been my home and I believe my future is in Fremantle.

"I would ask Bill Shorten to genuinely reassess the information used to disendorse my candidacy, so that I can continue in my campaign."

He said he could not comment further after receiving legal advice earlier on Thursday.

MUA 'angry' at treatment of Brown

Mr Cain said he was "very angry" at the way Mr Brown had been treated by the party "and they should all be ashamed of themselves".

He said the party "never wanted Chris Brown" and his disendorsement was a "fit up".

"The ALP was born out of the trade union movement and the trade union movement should have a bigger say in what goes on in it and we should start putting people back into the ALP from the grassroots — blue collar workers, transport workers, construction workers," he said.

Mr Cain said the MUA's ties with the party would remain, saying "our position's always been that we support the Labor Party".

The ALP's state executive has endorsed the Deputy Mayor of Fremantle, Josh Wilson, as Mr Brown's replacement.

Mr Brown has told the ABC he was charged with assault after an altercation at a festival in 1985 in which he made contact with a police officer, who had pulled him to his feet after he had been punched.

However he said the officer had later made a statement that the contact was accidental and he did not require medical treatment.

Wilson had local backing

Josh Wilson (L) has come under scrutiny on whether he backs the Labor Party's policy on asylum seekers. ( ABC News: Robert KoenigLuck )

Mr Wilson won the local ballot during the Fremantle preselection process 155 votes to 110.

However, because of the Labor Party's rules in Western Australia, the ballot of the state executive, which comprises political and union delegates, is given greater weighting in the preselection process.

Mr Brown won that vote 76 to 5, after gaining the support of the powerful left-aligned faction United Voice, who had initially backed Mr Wilson.

It is understood United Voice decided not to take on the MUA and other blue collar unions who backed Mr Brown over fears of making the party appear factionally driven and disunited.

Wilson says he supports Labor's asylum seeker policy

Mr Wilson said his thoughts were with Mr Brown and his family, and it was "humbling" to be asked to stand.

He also moved to dismiss suggestions he did not support Labor's position on offshore processing and turning back asylum seeker boats before they reach Australian shores.

"I look forward to a Labor government increasing our humanitarian intake by 100 per cent, doubling our humanitarian intake and importing the UN convention into domestic law, providing a specific commissioner to look after the interests of refugee children," he said.

"Those changes are incredibly important. They only happen under a Shorten Labor government."

Brown loses Shorten's support

Mr Shorten initially gave his backing to Mr Brown when he was preselected for Fremantle in March, saying at the time it was important to have diversity in politics and having MPs to represent the interests of working people.

However today he said he was disappointed by the events but supported the decision to drop Mr Brown.

"It is clear that the party processes were not followed, on very important matters," Mr Shorten said.

"The party has made a recommendation to me that he should not be the endorsed candidate. And I have absolutely supported that decision, 100 per cent."