National's energy spokesman Gerry Brownlee has defended himself against accusations he should have declared he had shares in Contact Energy.
Mr Brownlee had asked questions and given speeches which related to Contact and wider energy policy, the left wing Labour Party linked Standard website said.
Mr Brownlee owned shares in the company at the time and should have disclosed them, the website said.
Mr Brownlee disclosed the shareholding when the MPs register of pecuniary interests came into force in 2006.
The blog site said Mr Brownlee used his privileges as an MP to obtain information that gave him special information on the value of those shares.
Mr Brownlee told reporters today he had only a few hundred shares, which hardly amounted to a pecuniary interest.
He had transferred them to one of his children after taking on the energy portfolio for National.
Before the register of interests came into effect MPs were required under Parliament's rules to declare financial interests in certain circumstances, such as when debating legislation concerning those interests.
Such declarations have been very rare with various Speakers' rulings stating they were only necessary when business before the House had a legal effect and caused a benefit.
Various rulings have also narrowed the need for any MP to declare a financial interest, with one ruling stating that even holding a shareholding in a company which stood to gain from general legislation did not constitute a financial interest for an MP in dealing with that law change.