He said he was seeking legal advice before responding.
"I had thought that the matters concerning myself and Ms MacGregor had already been pretty well tested in the courts.
"However, the service of this paperwork does now trigger the legal process and I have a certain time in which to respond.
"As is required I will now do that. As this is a legal matter before the courts I will not be making any further comment at this time."
Yesterday, MacGregor said her legal action was a response to a defamation case Craig had filed against her.
"When media alerted me that Mr Craig had sued me I sought legal advice," she told the Herald.
"That advice was that I needed to file a document by today in order to protect my legal position.
"I will not be commenting further at this stage as the matter is before the court."
MacGregor resigned two days before the election in 2014, and made a sexual harassment complaint against Craig.
She later received an out-of-court settlement.
The current case adds to the tangled web of current legal action involving Craig.
Craig is currently suing Whale Oil blogger Cameron Slater, claiming that he defamed him in posts about sexual allegations involving MacGregor.
The case was heard at the High Court at Auckland, with the judge's decision still reserved.
Slater is counter-suing Craig for defamation over claims made in a booklet called Dirty Politics, which was distributed to 1.6 million homes.
Last week Radio New Zealand reported that Craig was planning to sue MacGregor for defamation if he lost the case against Whale Oil.
But Craig denied that report to the Herald, saying he had "historically" considered suing MacGregor but decided against it.
In response MacGregor said she had been advised that Craig's "failure" to serve those proceedings on her or her lawyers for several months was a breach of the High Court rules.
"It is unclear to me why Mr Craig would want to file proceedings but not give me notice of them.
"I strongly believe Mr Craig's claim against me is an abuse of process.
"Over the last year I have been dragged unwillingly into being a witness in two court proceedings by Mr Craig and others.
"I have been required to give evidence that was both highly personal and highly distressing.
"I would like to get on with my life."
After last week's events, MacGregor had invited Craig to "put an end" to the saga by withdrawing the proceedings.
