The government's asset sales bill has scraped through its second reading on a 61-59 vote after another ferocious attack from opposition parties.

The bill must become law before shares in four state-owned energy companies can be floated and it's getting a rough ride.

All the opposition parties oppose asset sales and they're going to delay the bill for as long as they can.

The government expects to raise about $6 billion from selling 49 per cent of the shares in Mighty River Power, Meridian Energy, Genesis Energy and Solid Energy.

Economic Development Minister Steven Joyce told parliament the alternative was to borrow the money and lead New Zealand into the sort of financial disaster Greece and other European countries were experiencing.

"The government is going to hold 51 per cent of the shares in these companies and no single shareholder can hold more than 10 per cent," he said as he rejected Labour's claims that they would end up controlled by foreign multi-nationals.

Labour, the Greens and NZ First argued the sale was economic madness and inter-generational theft.

They said there was no way the government could ensure the shares stayed in New Zealand ownership.

"The safeguards are bogus," NZ First leader Winston Peters said.

"All these shares will end up overseas and on election night 2014 government MPs are going to look back in agony."

Even National's ally, the Maori Party, voted against the bill and the government had to rely on United Future leader Peter Dunne and ACT's John Banks to get it through.

The second reading debate was capped at two hours but when the bill comes up for its committee stage next week there's going to be an open-ended free-for-all when every clause will be debated.

Opposition MPs are drafting dozens of amendments, and admit most of them are time-wasting ploys to delay the bill.