'I can't believe how liberal I am': Independent SA senator joins Liberal party

AAP

Independent South Australian senator Lucy Gichuhi has defected to the Liberal party in a surprise move giving the prime minister a much needed additional seat in the senate.

Prime Minister Malcolm Turnbull welcomed the new Liberal member to the party on Friday afternoon outside parliament.

"Those values - freedom, enterprise, getting ahead, opportunity - they are liberal values and you embody them ... welcome to the Liberal family," Mr Turnbull said in a video posted on Twitter.

An independent South Australian senator has joined the Liberal party giving Malcolm Turnbull an extra seat in the senate. Photo: AAP

Ms Gichuhi took the seat of Family First senator Bob Day following a vote recount after he was ruled ineligible to stand for election.

She then quit Family First after it merged with the Australian Conservatives.

In the social media video the new Liberal senator said she thought the move would help her serve South Australians.

"I didn't discover that until I did my maiden speech and I thought wow - I can't believe how liberal I am at the core," Ms Gichuhi explained.

The shock move has improved the Coalition government's position in the senate, bringing the total of seats to 29 to Labor's 25.

Ms Gichuhi took the seat of Family First senator Bob Day following a vote recount after he was ruled ineligible to stand for election. Photo: AAP

But the government will still need the support of the crossbench in order to pass legislation.

The defection is another boost for Mr Turnbull after the resignation of Labor MP David Feeney who was unable to prove he was no longer a British citizen.

The Greens are a big chance to win the by-election in Mr Feeney's seat of Batman, which would give the government some breathing space in the lower house where it currently holds a one-seat majority.