Labour MP David Parker says the magazine that accused him of filing false documents should apologise after he was cleared by the Companies Office.

Mr Parker looks set to return to Cabinet next week after an investigation found he did not lodge false annual returns with the Office.

He was the subject of an Investigate magazine cover story involving an allegation by a former business associate of Mr Parker, Dunedin property developer Russell Hyslop.

Mr Parker said after reading the article he felt the accusations were so serious that it was best he should resign, but it had been "scurrilous journalism".

Mr Parker said he had been given no opportunity to comment on the accusations before they were published or check whether they were correct.

"I was ambushed by these allegations," Mr Parker told National Radio.

It was impossible for him to stay on as Attorney-General -- the highest law officer -- while he was being investigated for breaking the law.

Mr Parker was still considering suing Investigate magazine for defamation, but he was sceptical, saying it was a long, expensive process that sometimes ended in 'barren" decisions by the court.

"At the very least I will have my lawyers contact him (the publisher Ian Wishart) and demand and apology," Mr Parker said.

Mr Wishart told National Radio he had not attempted to contact Mr Parker because Labour politicians had treated him badly in the past.

Mr Parker said ACT leader Rodney Hide had engaged in "gutter politics" in leading the charge against him and other Labour MPs in Parliament

"At the moment we have a climate where allegations are accepted as fact until they are disproved," Mr Parker said.

Mr Hide wished Mr Parker luck, but said Investigate magazine had been accurate and everyone knew he would be cleared because Prime Minister Helen Clark had sent a strong signal not to prosecute.

Helen Clark said the paper trail showed Mr Parker had done nothing wrong and that she would recommend to Labour MPs at their caucus meeting on Tuesday that he be re-elected to Cabinet.

Mr Parker quit his job as attorney-general and the portfolios of transport, climate change and energy.

Wishart said in a posting on the Investigate website that the legal opinion provided to the Companies Office was "seriously flawed" and raised fresh questions about its inquiry.