PAULINE Hanson's new One Nation senator has already quit the party just an hour being sworn in to the Senate.

Senator Hanson was conspicuously absent when senator Fraser Anning was sworn in to replace Malcolm Roberts today.

Senator Hanson has now released a statement saying Senator Anning has quit One Nation party and will stand as an independent "until something better comes along".

It will reduce the power of One Nation in the Senate, giving it three votes on the crossbench instead of four.

Senator Anning, who has been contacted for comment, is the second Senator to quit the party since it was swept to power in 2016.

One Nation Senator Fraser Anning was sworn in this morning, but was escorted into the chamber by Senators Cory Bernardi and David Leyonhjelm, rather than his party colleagues as tradition dictates.

Senator Hanson was absent from the chamber and the entrance caused a massive stir.

"Cory, did you get another one," a Labor Senator shouted to the Australian Conservatives founder Senator Bernardi.

Senator Hanson then released a statement claiming Senator Anning has "abandoned the party to stand as an independent".

There have been reports of strife between Senator Anning and One Nation and accusations the party asked him to stand aside to return Malcolm Roberts to the Senate.

In a statement, Senator Hanson said she asked Senators Burston and Georgiou to mediate with Mr Anning to find some common ground, but they were informed Mr Anning would stand as an Independent only minutes before he was sworn into the Senate.

She said prior to the High Court's decision, she had attempted to speak with Senator Anning, but those efforts "fell on deaf ears".

" I was forced to communicate through Fraser's brother while I was travelling through North Queensland in September.

"I indicated to Harry Anning at the time, that given the work Malcolm Roberts had achieved as Chair of the banking inquiry and his role in challenging climate change, it would be in the Federal Party's and Australia's best interest for Malcolm Roberts to be returned to the Senate.

"I was disappointed Mr Anning made no attempt to contact me or any One Nation executive member off the back of multiple requests to discuss his future plans."

She said she had approached Senator Anning to contest the state seat of Gladstone before the citizenship issues arose around Mr Roberts.

He receives 19 first preference votes, but filled the position left vacant by former Senator Malcolm Roberts's being found to be ineligible by the High Court as part of the citizenship scandal.

The two One Nation Senators in the chamber did not appear to congratulate their new colleague, instead shaking hands with the new Greens Senators sworn in today.

Senator Leyonhjelm issued a statement saying: "Senator David Leyonhjelm vouched for new One Nation senator Fraser Anning in the chamber this morning, in the company of Senator Bernardi. Senator Leyonhjelm did so with pleasure at the invitation of Senator Anning."

Also sworn in today was new Greens Senator for Queensland Andrew Bartlett, replacing former Senator Larissa Waters who resigned as part of the citizenship scandal.

Also sworn in was new WA Senator for the Greens Jordan Steele-John, a disability advocate and the youngest Senator elected at age 23.

Former Australian Democrat Andrew Bartlett was also sworn in today to replace Larissa Waters for the Greens.

Meanwhile, Malcolm Turnbull will be forced to reshuffle or cut back his cabinet by one after Special Minister for State Scott Ryan was elected as the new Senate President.

It comes after former Senate President Stephen Parry's bombshell announcement earlier this month that he was a British citizen by descent.

Independent senator Jacqui Lambie and Nick Xenophon Team MP Rebekha Sharkie have also come under the spotlight.

Prime Minister Malcolm Turnbull has threatened to refer the Labor MPs in question to the High Court, demanding that Bill Shorten stop running a "protection racket" for the potential dual citizens in his party.

The Opposition has today released new legal advice that Ms Sharkie and Labor MPs Justine Keay and Susan Lamb are eligible to sit in Parliament because they took all reasonable steps to renounce their foreign citizenship before they submitted their nomination to be a candidate in the 2016 election.

Victorian barrister Peter Hanks QC advised Labor that the trio took all necessary steps required by United Kingdom law to renounce their British citizenship.

"From that time on, the formalities of completing the process of renunciation were out of their hands and subject to the vagaries of the administrative processes in the United Kingdom," he said.

"The taking of those steps by the three Australian Citizens was sufficient for the purposes of s 44(i) of the Constitution to ensure that, from that time on, each of them was not incapable of being chosen as a member of the House of Representatives."