Monaco-based billionaire Owen Glenn flew into Auckland yesterday and will give evidence to the committee in Parliament this afternoon.
Mr Glenn says NZ First leader Winston Peters personally solicited the donation to help pay his lawyer's fees, and later thanked him for it.
Mr Peters says he never asked Mr Glenn for money, and the request was made in a phone call from the lawyer, Brian Henry.
Mr Glenn made the donation in December 2005, Mr Peters says he knew nothing about it until Mr Henry told him in July this year.
The committee asked Mr Glenn to appear personally after he sent it a written statement saying there was no way he would have given the donation if it had been asked for by an intermediary, and he was sure the request came from Mr Peters.
The status of the donation is important because NZ First did not declare it.
The party says it was a payment made to Mr Henry, and did not have to be declared.
The committee has to decide whether paying the fees amounted to a gift, in which case it should have been declared.
But the cheque is only one of NZ First's problems -- last night the police confirmed there would be an inquiry into another undeclared donation.
ACT leader Rodney Hide laid the complaint about the $80,000 donation, which he says should have been declared in the party's 2007 return to the Electoral Commission.
The Serious Fraud Office is holding a separate inquiry into a $25,000 donation from Sir Robert Jones, and cheques from the wealthy Vela family, to find out whether the money was used for the purposes the donors intended.
And yesterday the commission gave NZ First a September 30 deadline to file accurate returns for 2005, 2006 and 2007.
It also wants a detailed account of why the party sent in nil returns for those years.
