NZ First leader Winston Peters has come up with a cost-saving solution to Parliament's looming space problem: cut the number of MPs to 100 instead of spending millions on a new office block.

Parliament's Speaker David Carter has proposed building a new office block on Parliament's grounds to house MPs and staff after the lease of Bowen House ends at the end of 2018.

Carter told Fairfax Media he believed Parliament should own its own buildings rather than continue to lease Bowen House at a cost of about $6 million a year.

The Government has been consulting Opposition parties on the proposal and Peters said it did not have his backing.

"At a time when there are well over 40,000 Kiwis homeless and young Kiwis struggling to buy a home, it ill behoves parliamentarians to consider their own comforts.

The fact is we don't need Parliamentarians, 100 would be sufficient, at which time we would have plenty of room."

Peters said the public of New Zealand had voted to reduce the number of MPs back to 99 in a referendum in 1999 but it was never acted on. 

After New Zealand adopted MMP it went from 99 electorate MPs in 1993 to 120 - a mix of electorate and list MPs.

NZ First believed it should be acted on given 81.5 per cent had supported the cut in the referendum.

He said some ministers could also consider cutting the number of staff they had to free up space.

"Former Prime Minister Keith Holyoake used to have five people in his office - Prime Minister John Key has 55. Before anyone starts screaming about the need for more space let's take a look at how bloated the system now is."

Those staff numbers included the Prime Minister's Office as well as the Department of Prime Minister and Cabinet.

He said it was a National Government which sold Bowen House in the 1990s and it was now paying the price.

"As usual the taxpayer is being hit hard by the decision of National to sell state assets."

Bowen House is home to a handful of ministers as an overflow from the Beehive, as well as the smaller parties - the Maori Party, Greens, Act, United Future and NZ First.

There are currently 121 MPs - United Future leader Peter Dunne is an electorate MP but United Future party vote was not enough to qualify for an MP, resulting in an overhang.​

- NZ Herald