New Zealand's leading business lobby groups say the Labour Party and the Greens have "ambushed" businesses with their controversial electricity policy which they claim sets a "disturbing precedent" for further intervention.

Labour and the Greens have defended their controversial electricity policy after New Zealand's business leaders issued an open letter asking them to withdraw it.

Insurance will represent a significantly higher share of the cost of living and the cost of doing business from here on, writes Brian Fallow.

Labour MP Shane Jones says he was a "doubting Thomas'' on the Labour - Greens police to lower power prices, but now fully backs the plan.

In the week or so since it revealed its plan to slash power prices, Labour has bared its teeth at anyone questioning the wisdom of breaking up the wholesale electricity market just as it is showing signs of functioning as intended.

The Labour-Greens' proposal has created a major dilemma for potential Mighty River Power investors - should they invest in a company that could be subject to major regulatory change, including a dramatic adjustment to its business model?

If Meridian Energy had already floated, it's a fair bet that its share price would have dropped after the Opposition unveiled its electricity policy a week ago.

The onus is on those calling for radical, disruptive change to something as important as the electricity sector to demonstrate that it is broken and needs fixing.

The Labour-Green proposal aims to stop electricity generators 'gaming' the market in search of higher prices. Adam Bennett investigates.

"What just happened?" asks Brian Rudman. "Bland, colourless Labour leader David Shearer has suddenly been transmogrified into a working-class hero."

Investors who applied for Mighty River Power shares have been given a deadline to withdraw their applications if concerned about the Labour-Greens' power policy plans.

The Government said it would file a supplementary disclosure to the Mighty River Power share offer to take into account possible additional risks to investors that electricity reform under a Labour/Greens government could pose.

As Mighty River Power's boss prepares the State-owned company for sale, he has slated the new Labour-Green electricity policy as "socialist".

Uncertainty created by the Labour Party and Greens' plans for the electricity market helped drive the share prices of the main NZX-listed power generators sharply down yesterday.

Millions of dollars of NZers' savings have been wiped after Labour and the Greens announced plans to reform the wholesale electricity market, the Government says.

Humankind can be divided into two categories: those who understand the complexities of the wholesale electricity market and those who do not, writes John Armstrong.

The Labour-Green proposal to cut Kiwi householders' power prices through radical market reform has been given the thumbs-up by consumer groups, but energy sector commentators are divided on the plan.

Editorial: Labour proposes to set up a single buyer, NZ Power, to purchase all electricity generation at what it deems a fair price, based on the actual cost of production.

Labour and Greens want Crown-owned single buyer to set electricity prices for generators.

Electricity prices were a conspicuous exception to the subdued inflation numbers reported yesterday.

New Zealand could face power shortages this winter unless the hydro lakes get a significant boost soon.

Mighty River Power has warned would-be investors of a long-term drop in electricity prices which would hit the value of its shares should the Tiwai Point aluminium smelter close.

The Government has set a price range of $2.35 to $2.80 per share for the partial privatisation of Mighty River Power.

Almost 180 Christchurch landowners have chosen not to accept the Crown offers on their red-zoned properties.