National MP Pansy Wong's husband, Sammy, conducted business while on a taxpayer-funded trip to China at least twice, Labour MP Pete Hodgson claims.

An independent investigation of travel claims by the Wongs was ordered by Speaker Lockwood Smith after it was revealed that on a trip to China in 2008, Mr Wong was involved in a business deal.

That trip was made with a 90 per cent taxpayer-funded rebate on their airfares, and it is against the rules to use the allowance for private business.

The report covered claims for the past 10 years and found no evidence the rebate had been misused on other occasions.

Mrs Wong has apologised and paid back the $474 rebate for the China trip. She earlier resigned as minister when the allegations came to light.

Mr Hodgson told Parliament today Mr Wong had conducted business on a second trip, despite telling investigator Hugh McPhail the trip was for genealogical research.

"Is he aware that in June 2005 Sammy Wong travelled, using taxpayer funding, to Fujian Province," Mr Hodgson said in questions to Prime Minister John Key.

"On the morning after arrival he helped former Prime Minister Jenny Shipley launch a $40 million investment into a biotechnology centre, in which Mrs Shipley has shares, but that he told Mr McPhail that the reason he went to Fujian Province was for genealogical research."

Mr Key said he was not aware of it.

"... if any members have any information that they want to send off to the Auditor-General, they are free to do so," he said.

The Labour Party has called for an Auditor-General's inquiry into Mrs Wong's travel expenses.