The National Party claims the government has been aware about a possible power shortage this winter for three years.
Gerry Brownlee says there were warnings from the Electricity Commission in 2005 that there was an unacceptable risk to the power supply because of the condition of the Cook Strait cable.
Brownlee says Energy Minister David Parker has known about the deterioration of the link for years and nothing has been done to fix it.
"In 2005, Labour's Electricity Commission was considering a significant plan to repair the Cook Strait cable by 2010. In the conclusion the documents say the medium term 'risk profile is unacceptable.
"Yet, last week David Parker said the partial shutdown of the cable was a 'surprise' and Helen Clark said yesterday 'eyebrows have certainly been raised'," says Brownlee.
The government is playing down the threat of power cuts, saying work is being carried out on having the Cook Strait cable operating more effectively.
The cable was closed because the line linking the North and South Islands because it had become so old and degraded that it could no longer be used safely.
Moves are now afoot to repair the cable and re-open it, but a critical report from global credit rating agency, Fitch Ratings, blamed a stand-off between Transpower and the Electricity Commission for delays in replacing the vital high voltage link between the two islands.
Low levels in hydro lakes, high water temperatures restricting the use of the Huntly power station and wind farms failing to spin have also caused concern about winter power supply.