Former Conservative Party head Colin Craig has filed papers in the High Court in Auckland to sue his former press secretary for defamation.
Mr Craig has confirmed to RNZ the papers have been filed against Rachel MacGregor but said the case would only go ahead if his case against Cameron Slater did not go in his favour.
That case finished last week, with Justice Toogood reserving his decision.
In that case, Mr Craig sued Mr Slater for posts he made on his Whale Oil blog about Mr Craig and his relationship with Ms MacGregor. Mr Slater counter-sued Mr Craig for statements made in a leaflet sent out to 1.6 million households around the country.
Ms MacGregor said she was not aware of the new proceedings until contacted by RNZ.
She said she had not been served with documents, and declined to comment.
Her advocate, Ruth Money, said the action showed Mr Craig's "true colours" and declined to comment further.
Mr Craig said he would not go into details about the case but confirmed it was a defamation proceeding.
New lawsuit one of at least five before the courts
Mr Craig said he has taken what he called a "limited approach" in his defamation cases. So far he has sued Mr Slater and a board member of the Conservative Party, John Stringer.
He said people had said a lot of things about him that were not true and he wanted to establish the facts.
His case against Ms MacGregor is one of at least five before the courts at present.
Last year the head of the taxpayer's union, Jordan Williams, sued Colin Craig over comments he made about Mr Williams in a booklet sent to 1.6 million households around New Zealand.
The jury found in Mr Williams' favour and awarded him $1.27 million in damages - the highest amount ever in a New Zealand defamation case.
That was reviewed by the trial judge, Justice Katz, who found it to be excessive. Both parties are appealing.
Mr Craig has also sued John Stringer, a former board member of the Conservative Party. That was settled out of court but Mr Stringer is now bringing another case against Mr Craig.
Mr Craig has also sued Cameron Slater over copyright in the Auckland District Court, after Mr Slater published Mr Craig's poems on his blog. Mr Craig lost the case. He is also appealing against that decision to the High Court.
Lastly, there is the defamation case against Cameron Slater which concluded last week.
Rachel MacGregor's previous appearances
Ms MacGregor has given evidence at two of these trials. She was subpoenaed to give evidence for Mr Slater and was later cross-examined by Mr Craig.
Ms MacGregor spoke of getting what she described as "creepy" poetry from her boss.
She also described the poems as "dodgy" and said they made her feel awkward and disgusted.
She said she and Mr Craig had a dispute over her hourly rate and that Mr Craig then paid her two $10,000 advances and loaned her $18,000.
Ms MacGregor said when she resigned, Mr Craig enacted a clause that allowed him to charge her 29 percent interest.
She accused him of putting financial pressure on her to have sex with him - something Mr Craig denied.
Ms MacGregor resigned days before the 2014 election and filed a sexual harassment complaint that was eventually settled and Mr Craig later stepped down as leader of the Conservative Party.