Any attempt to scrap former MPs' international travel perk would almost certainly result in legal action, Prime Minister John Key says.
Parliament's Speaker, Lockwood Smith, has taken it away from sitting MPs but more than 100 former members still have a life-long entitlement to the taxpayer-funded allowance which pays for up to 90 percent of their international air fares.
Dr Smith announced his decision last night, saying it wasn't justified for current MPs and he hadn't addressed the question of whether it should be removed from former MPs.
"There are all sorts of issues regarding the remuneration of former members," he said.
Mr Key agreed with that today, saying he was pleased the perk had been taken away from current MPs but it would be very difficult to act against former members.
"It would be very challenging if we wanted to get rid of it, there would almost certainly be legal action taken against us," he told reporters.
"We would be re-writing history...we could always legislate but the ex-mps association has made it quite clear they would fight any attempt to take it from them."
The next issue that has to be resolved is whether MPs should get a pay rise to compensate them for losing the travel perk.
That will be up to the independent Remuneration Authority which sets their salaries and conditions.
Mr Key said it had previously sought feedback from him.
"They've written to me about increasing MPs' salaries and I've written back saying my recommendation is zero," he said.
"I've also said that if they're really hellbent on increasing MPs' salaries my view is there should be a very modest increase -- I don't think MPs can justify getting lavish pay increases when the rest of the country is living off 1 percent and 2 percent pay increases."
Dr Smith made his decision to scrap the allowance for sitting MPs after meeting representatives of all the parties in Parliament, who backed the move.
The allowance has been an issue since former cabinet minister Pansy Wong resigned her portfolios because she broke the rules when she and her husband used the allowance -- a 90 percent rebate in their case -- for a trip to China.
Her husband, Sammy Wong, was involved in a business deal while they were there and using the perk for anything other than private travel is forbidden.
An investigation is underway into all Mrs Wong's previous travel claims.