In a further blow to the Mighty River Power share offer's likely success, the Government has had to issue a supplementary disclosure document.
It outlines the likely impact of the Labour/Green parties' new electricity policy, should they be able to form a government after the next election.
The document says the regulatory uncertainty is likely to have a material adverse effect on the value and market price of Mighty River Power shares but the Government can't quantify that impact.
Labour and the Greens plan to establish a single buyer of wholesale electricity which they claim will result in total savings to consumers of between $500 million and $750 million a year.
BT Funds Management portfolio manager Matthew Goodson said the situation will depress the price of Mighty River Power shares.
He said the share prices of the already listed companies Trustpower and Contact Energy have fallen by as much as 10% and they now seem to be about 5 - 7% lower than they were immediately prior to the Labour/Green announcement.
Mr Goodson said BT Funds Management is in the process of assessing the affect on the Mighty River Power share price and will not comment on precise numbers.
"But you know we do have that market evidence, Contact and Trustpower do have slightly different business mixes to Mighty River, but they nevertheless perhaps give an accurate signal of the market's current verdict."
Fisher Funds chief investment officer Mark Brighouse said investor confidence has been dented.