Official documents suggest immigration officials were pressured from the top to ask for more money to stop boat people.

In February, Immigration New Zealand tripled its bid for Budget funding to prevent "maritime mass arrivals" - from $11 million dollars over four years, to $33 million.

Emails from the head of Immigration just weeks earlier say the Prime Minister and Minister of Immigration had given them a "strong steer" to not understate mass arrivals in the budget.

Immigration consultant Howard Levarko told Mike Hosking the move is excessive, especially when there are so many other issues at Immigration.

"Part of this extra $20 million could be better spent addressing staff issues and systemic problems on shore and offshore branches rather than going down this other track."

Lees-Galloway has defended the funding, saying people-smuggling is of increasing concern both internationally and regionally.

The money was approved despite objections from the Treasury, which denies the current system is inadequate.