Ex-MP Taito Phillip Field has told a court he was unsure if letting overstayers stay at his house was illegal and says he didn't ask them to make renovations while there.

Field let Phisamai Phothisarn and her partner Sompong Srikaew stay in his Prangley Ave, Mangere, house because they were in a "desperate situation", had a young child and needed a place to stay.

Crown prosecutor David Johnstone put it to Field that he allowed them to stay at the house so they could hide from the Immigration Service, but Field denied it.

"That was not the reason. I didn't see it that way," Field replied. While the couple lived there they carried out some renovations but Field said he didn't tell them to do maintenance.

The former Mangere MP is defending 12 counts of corruption and bribery as an MP and 23 counts of perverting the course of justice. His trial at the High Court at Auckland is into its 15th week.

When told it was very convenient they worked on the house, Field said: "We never told them to do it initially. [They stayed] purely on the basis they needed somewhere to stay temporarily".

He attributed the fact they did work on the house as being grateful for living at the house rent free, and not for help he was giving them on their immigration status.

About the time they stayed at Prangley Ave, Field wrote to the Associate Immigration Minister and the Immigration Service for them.

"I did not see it as a bribe ... friendships developed. It was friends helping friends." Any suggestion of a cover-up was "totally untrue".

Field said he didn't think he was breaking the law by letting them stay but he wasn't sure.

Mr Johnstone said it was against the law.

Field said people who came to his electorate office seeking help were reminded that gifts, in thanks, were unacceptable. Sometimes gifts of money were donated to the church. A sign told visitors advice and services were free. After questioning Field acknowledged the sign could have been put up after Parliamentary Services staff visited.

During his testimony Field had to be reminded by Justice Rodney Hansen to answer the question.

"You'll have ample time to qualify your answer if it is required."

Earlier, Field told defence lawyer Paul Davison QC he was "clear in his mind" that he was not guilty of bribery or corruption.