Ms Kitching, a key ally and friend of Mr Shorten, was parachuted in to fill the Senate vacancy created by the retirement of Stephen Conroy, with the Opposition's Leader support, on Friday.

But in a thinly veiled reference to the behind-closed-doors decision to install Ms Kitching to the role, Mr Albanese – a former deputy prime minister who stood against Mr Shorten in the 2013 leadership contest – said ALP members should be given a greater say in Senate preselections.

Mr Albanese also slapped down Victorian Labor senator Gavin Marshall, who on Monday foreshadowed he would work to unseat Albanese ally and Labor MP Andrew Giles and possibly frontbench health spokeswoman Catherine King.

Ms Kitching was on Thursday selected unopposed by Victorian Labor's 100 person Public Office Selection committee for the casual Senate vacancy, which will see her serve almost all of the six-year term. Mr Shorten's support for her is seen as key to her securing the plum spot.

Her selection has triggered concern in some sections of the ALP. The federal government has used Ms Kitching's selection and the fact that she was referred for "further investigation" by the Heydon royal commission into trade unions to attack the Opposition Leader and make the case for the passage of its bills to re-establish the construction industry watchdog and the establishment of a Registered Organisations Commission to monitor unions.

Mr Albanese, who had pushed for Labor party reforms in the 2013 leadership contest, repeatedly refused to endorse Ms Kitching's preselection on Tuesday, pointing out that as a NSW MP he did not have a say in Victorian matters.

"I didn't have a vote, I'm not familiar with all of the candidates, that's a matter for the Victorian branch," he said.

"Quite clearly she [Ms Kitching] had the support of some significant figures from the Victorian branch and that's a matter for them. I support ensuring that preselections are held in accordance with the rules. This one, that certainly happened [but] I think there certainly is a case for ensuring that members have votes in Senate pre-selections. That's something I have supported on the record across the board for some time as a part of party reform."

Asked directly if he endorsed Ms Kitching, who will soon sit in the same caucus room, Mr Albanese said: "I don't know all of the candidates, therefore I wasn't in a position to make a judgment."

The NSW branch of the ALP is more democratic than the Victorian branch, with Senate candidates chosen publicly at the party conference; the Victorian committee chooses candidates behind closed doors.

Following Senator Marshall's attack on Mr Giles and Ms King, an informal process is now under way involving Mr Shorten and other senior figures in the party to heal a split in the Left faction that has seen a Victorian "industrial" Left, led by senators Kim Carr and Marshall peel away from the national Left faction, which is led by Mr Albanese and South Australian MP Mark Butler.

Mr Albanese said Senator Marshall's comments " speak for themselves, they say more about Senator Marshall than they do about the colleagues he is disparaging".

"I have seen the comments about not just Andrew Giles but Catherine King and Jenny Macklin. They are all valued colleagues, they are all frontbench colleagues, they are all playing a significant role in the Parliament and they have I think the support of everyone – not just here, but importantly the people in their respective electorates, which is why they were all returned on July 2."

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