UPDATED 4.31pm: Members of Parliament aren't going to get their pay rise after all.

The Prime Minister will change the law under urgency to stop the average three and a half percent pay rise handed out by the Remuneration Authority last week.

Any back pack pay they get will have to be repaid.

John Key says the public sector have got between one and two percent and the MPs should be no different.

"We expect them to show restraint, that's the government living within its means.

"We've been making that case incredibly plainly and clearly to the Remuneration Authority and what's clear this time is that pay increase they suggested this time didn't reflect that."