Prime Minister Bill English once described Middle Eastern asylum seekers as "leftovers" who should be blocked from entering New Zealand.

Just over 10 years ago he criticised then-Prime Minister Helen Clark as being a "soft touch" on migrants - and promised a National Government would "turn the green light red".

"New Zealand is now seen as a soft touch for other fascists, terrorists, whoever is on the losing side in bad regimes, unwanted at home and unable to get into any other country," he said.

The comments were written in a National Party newsletter by Mr English on May 9, 2005. He was discussing the case of Ahmed Zaoui - an Algerian refugee who had been granted asylum, despite being identified as a security risk by the SIS.

"If you turn up to the border with an apple, you get done. If you turn up with an Iraqi passport and references from Saddam Hussein, you get in," wrote Mr English.

"We need migrants, but we don't need leftovers from Middle East terrorist regimes," he said in the 2005 newsletter.

Mr English finished the spiel by saying the green light Labour had sent to the world would "certainly" be turned red by National.

Asked about his comments at a news conference on Wednesday, Mr English says the Government is "taking the practicable steps we can to mitigate those risks, you can't eliminate them".

"Part of the job of our security structure is to identify where those risks come from to prevent them creating problems in New Zealand and that was the case then and is the case now.

"Well, you don't need terrorists here and if one turns up at the border with a reference from Saddam Hussein or other terrorist credentials then they won't be allowed in."

The Security Intelligence Service had once linked Mr Zaoui to a terrorist group, but he was eventually granted New Zealand citizenship in 2014.

Mr English believed that had Mr Zaoui arrived in New Zealand today, the current border security measures in place "would probably not allow that to happen".