Former Cabinet minister Taito Phillip Field got several Thai nationals to work on his houses for little or no money in exchange for immigration help and then tried to derail investigations into them, a jury has been told.

Crown prosecutor Simon Moore was addressing the jury on the first day of the trial in the High Court at Auckland of Field, who faces 35 criminal charges.

Field, the MP for Mangere between 1993 and 2008, has pleaded not guilty to 12 bribery and corruption charges and 23 charges of wilfully attempting to obstruct or pervert the course of justice.

Mr Moore said that as an MP, Field was paid a salary to serve the community and was not allowed to accept any extra payments for work which was part of this job.

This included work which Field did on behalf of several people who came to him for help because they had problems with their immigration status.

But between 2002 and 2005, Mr Moore said Mr Field received benefits from several Thai people in return for his help with their immigration issues.

"The benefits Mr Field received were not in the form of money. The benefits were in the form of work which he had done on various houses which he owned in New Zealand and a large house he owned in his country of birth, Samoa," Mr Moore said.

"The work was in the form of painting, plastering, and in Samoa, tiling.

"The Thai men and women did this work because they wanted Mr Field to help with their immigration problems, or because they were grateful for the work he had already done."

Mr Moore said the 12 bribery and corruption charges were laid in relation to this work.

The remaining 23 charges came after allegations about the work on his houses emerged in media shortly before the 2005 election.

Prime Minister Helen Clark set up an inquiry into Mr Field's conduct, headed by Auckland barrister Noel Ingram, and Mr Moore said Field publicly stated he would co-operate fully with the inquiry.

"But far from co-operating, he took deliberate steps to do the exact opposite," Mr Moore said.

He said Field arranged for false evidence to be placed before the inquiry, arranged for false receipts and documents to be created in relation to the work, and got the Thai workers "to lie on his behalf".

The trial began today after it took 2-1/2 days to ensure a jury was empanelled for the 12-week trial.

Seven of the original 12 jurors empanelled on Monday were discharged by Justice Rodney Hansen yesterday, forcing seven new jurors to be empanelled today.

Justice Hansen asked all potential jurors to speak to him before they headed for the jury bench to see if there was any reason why they could not sit on the jury.

He was not able to begin his opening statements to jurors until 12.25pm today, and Mr Moore began his opening address at 2.20pm.

Field was elected as a Labour MP for Mangere in 1993 and rose to be a cabinet minister. He was expelled from the Labour Party in 2007 and continued to represent Mangere as an independent MP before losing the seat to Labour at last year's election.