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Budget: 2000 hack attempts of Treasury website over 48 hours
PM Jacinda Ardern refused to offer Treasury her full confidence following Budget 'leak'
Government concedes some of National's Budget 2019 details correct
But Makhlouf would not or could not confirm whether National's Budget information had come from the Treasury website.
And Mitchell said it appeared the hack and the leak were two unrelated events. He told Hosking he was disturbed that Treasury had not picked up the hack when it happened.
He said the Government was using the opportunity to "smear" the Opposition.
On the same programme Labour MP Stuart Nash said the use of hacked material would be "dirty politics" but that legitimate leaks were fair game.
He said the first thing he would always do when given leaked information was ask where it had come from.
"If someone said to me, 'Well it was leaked by a disgruntled staffer,' then you go 'OK, game's on'.
"If it was said it was gained by illegal method, then you go 'Well I'm not going near this'. I think the first thing that Simon Bridges or his team or National would have asked is, 'Where did this information come from?' "