Senator Dastyari's replacement in the Senate will not be selected by NSW Labor until the start of February. That person – widely tipped to be Kristina Keneally, if she does not win the seat of Bennelong in a byelection this Saturday – will then have to be confirmed by the NSW Parliament.

Senator Dastyari quit over revelations in Fairfax Media over his links to Chinese Communist Party-linked political donor Huang Xiangmo; his exit has infuriated allies of Senator Dastyari in the influential NSW Right faction of the ALP, which has loyally backed Mr Shorten as party leader since 2013.

When announcing his resignation on Tuesday, Senator Dastyari did not immediately stand down, but said he would "not return to the Senate in 2018". Parliament is not due to return until February 5.

If Senator Dastyari did not formally resign until February, he would continue to draw his senator's salary, which would amount to about $20,000.

However a well-placed Labor source said Senator Dastyari would be gone within a matter of weeks.

Prime Minister Malcolm Turnbull said Senator Dastyari should "get out of the Senate right now and it is a mark of the weakness of Bill Shorten's leadership that it took all of this time for Dastyari to foreshadow his resignation".

"He hasn't resigned yet. He's still taking money from the taxpayers of the country that he put second. He did not put Australia first."

But Mr Shorten argued other MPs who had quit parliament had taken lengthy periods to go, too and that Senator Dastyari was no different.

"[Liberal] senator Brett Mason – 23 days. Christine Milne, leader of the Greens – 98 days. Joe Hockey – 34 days. Then he moved onto another paid government job. [Liberal] senator Michael Ronaldson – 73 days. [Liberal] senator Chris Back, admittedly not a household name, but 46 days. Even Nick Xenophon – 26 days," he said.

"What I expect Senator Dastyari will do is that, sooner rather than later, he will wrap up his matters. But let's be clear – there's electorate work. He can't just leave punters in the lurch. He's resigning. He won't be back in the Parliament."

NSW Labor general secretary Kaila Murnain said the party would "begin the process of selecting for the Senate casual vacancy early next year. There are a number of administrative processes that have to be completed, which can't be finalised prior to Christmas."

Some MPs believe Senator Dastyari could have survived the scandal if he had hung on until Christmas, and that he was unfairly treated by Mr Shorten and sections of the Labor Left faction.

Finger pointing has begun, with some members of the Right suggesting a co-ordinated attack was launched on Senator Dastyari to force him out.

A report that Senator Dastyari pressured deputy Labor leader Tanya Plibersek not to meet a pre-democracy activist in Hong Kong, which was quickly followed by senior Left MPs Catherine King and Linda Burney suggesting he should consider his position, has been blamed as the final straw before Senator Dastyari's demise.

"Sam was pushed, and pushed in the worst possible way – by being leaked against by his own people. It looked like a co-ordinated campaign," one MP said.

None of us were deluded about the extent to which this has hurt us but I'm not aware of anyone in the Right who did think he should go. He deserved more support."

Mr Turnbull and Mr Shorten both campaigned in Bennelong alongside John Alexander and Ms Keneally, respectively, and traded blows over health funding, China, and Ms Keneally's record as premier.

The Prime Minister acknowledged that Bennelong was a high stakes contest as he will lose his majority in Parliament if the ALP wins.

"If Labor were to win in Bennelong, then Bill Shorten would become very close to becoming prime minister. We can't afford to have a Shorten government," he said.

Labor sources say Ms Keneally trails Mr Alexander 48-52 or 47-53 in the two-party preferred vote, according to internal party polling.