Key Points:

A Serious Fraud Office (SFO) investigation into New Zealand First has cleared the party of fraud, but party leader Winston Peters isn't going to get his ministerial portfolios back before the election.

He stood down as minister of foreign affairs, and other portfolios, when the SFO announced in August it was going to investigate donations to his party.

Prime Minister Helen Clark took them over, and she said tonight she would continue to hold them because other inquiries were still being carried out and the election was close.

"We are all seeking a fresh mandate at the general election," Miss Clark said.

Mr Peters said the investigation had been a waste of time.

There was never anything to be investigated, Mr Peters said. He blamed Act Party leader Rodney Hide for the investigation going ahead in the first place.

"The only complainant in this sorry episode was a sad little man in a yellow coat, so desperate for attention that he used a tawdry stunt to tie up the resources of an agency that should have been investigating serious corporate crime," Mr Peters said.

"My advice to the SFO is to go and find some real crooks."

The SFO announced in August it would investigate donations to NZ First from Sir Robert Jones and the Vela family to find out whether they were used for the purposes the donors intended.

SFO director Grant Liddell said there was no basis for fraud charges to be laid, but the way donations were channelled through the Spencer Trust may have broken other laws.

"We have found information showing that the laws relating to election returns may not have been complied with," Mr Liddell said.

"Information shows that NZ First's donations returns and the auditor's reports on those returns for 2005 and 2007 appear to be inaccurate.

"The party's election return for 2005 also appears to be incomplete."

Mr Liddell said information had been passed onto investigations currently underway by the Electoral Commission and police.

NZ First had provided "all the relevant information" to the commission and police, Mr Peters said.

He hoped the matter would be quickly resolved.

NZ First would continue with its complaint to police that some SFO officers misused their powers in reporting information to politicians on the privileges committee.

Behind closed doors, the committee considered SFO evidence relating to Mr Peters' claim he paid back his lawyer $40,000 in court-ordered costs from his failed Tauranga electoral petition.

Mr Liddell said SFO investigations showed Mr Peters appeared to have received a gift in the year to January that should have been declared on the Register of Pecuniary interests for MPs.

"The Spencer Trust made payments on behalf of Mr Peters to settle litigation. The payments were funded by a donation to the Spencer Trust."

That information had been provided to the Auditor-General, who audited members' returns to the register.

"I have written to Mr Peters asking him to consider this information and determine whether he should file an amended return to the Register of Pecuniary interests," Mr Liddell said.

The SFO had worked as quickly as possible on the investigation in the interests of all the parties concerned, he said.

"The issues raised are now matters for other agencies to address."