One Nation MP Mark Latham says he has been ousted as leader of the party in New South Wales.

Mr Latham said in a Facebook post federal leader Pauline Hanson removed him from the job "without consultation or due process".

"Senator Hanson has installed a new state executive with no leader," he said.

Mr Latham remains a member of the One Nation party.

In a statement, Senator Hanson said the party chose to appoint a new leader in NSW "following the recent state election which saw [the party's] vote drop by 14 per cent".

"The national executive of the party has also declared vacant the position of NSW parliamentary leader while the review takes place," the statement read.

Mr Latham, however, said he remained the leader of the "parliamentary team".

"This is a matter, quite rightly, for me, Rod Roberts and Tania Mihailuk. I remain as the leader of our parliamentary team," he said.

"Over the past 5 years we have built up into the largest One Nation parliamentary party in the country— so where’s the problem?"

It comes after a rift between the pair ignited when Independent MP Alex Greenwich sued Mr Latham in May for defamation, alleging comments he made portrayed him as not being a fit and proper person to serve parliament. 

Senator Hanson at the time admonished the remarks by Mr Latham.

"I want you to know that I don't condone them [the comments], and neither do my members of parliament or party associates," Ms Hanson said in a video statement.

"I think they are disgusting."

Mr Latham in March posted, and then deleted, a graphic tweet directed at Mr Greenwich. 

Mr Latham began his parliamentary career in national politics in 1994 as the Labor Party as the Member for Werriwa.