Xenophon may have farewelled Senate

Crossbench senator Nick Xenophon may have made his last speech to the Senate, ahead of the High Court handing down its ruling on the seven politicians under a citizenship cloud.

"I do not know when I'll be making my last speech to the Senate, I hope this won't be it because I have a lot to say about many issues affecting my home state of South Australia," Senator Xenophon said during a adjournment debate speech on Wednesday night.

Under section 44 of the constitution "a subject or a citizen ... of a foreign power" cannot stand for parliament.

The High Court has been considering doubts over Senator Xenophon citizenship status - his mother was born in Greece and his Cyprus-born father held a British passport.

"I will be leaving this place one way or other, sooner rather than later," Senator Xenophon said, before discussing what he sees as the unfinished business of political donation reform.

Senator Xenophon earlier this month announced his bid to return to South Australian state politics.

There's a chance his SA-Best party could win the balance of power in the state parliament.

Attorney General George Brandis joked it was out of character for Senator Xenophon to deliver his potential farewell speech in a non-flamboyant discreet way.

"While we do not wish you success in the South Australian election... nevertheless on behalf of the government I did want to wish you well in a personal sense," Senator Brandis said, adding his time in the Senate had been very consequential and he had dealt with the government in a considerate and constructive manner.

Labor's senate leader Penny Wong said the Senate won't be the same with out him.

"I do wish you well," she said.

It's unclear when the High Court will hand down its ruling.

Eligibility for parliament is also in doubt for the Nationals' Barnaby Joyce, Fiona Nash and Matt Canavan, former Greens senators Scott Ludlam and Larissa Waters and One Nation's Malcolm Roberts.

Next week senators will be grilling public servants at Senate estimates hearings.