The Government is being accused of not backing local industry after it emerged an Australian company designed the website for its Mighty River Power share offer.
Prime Minister John Key has long promised New Zealanders will be "front of the queue" for buying shares in state owned enterprises, but the Green Party said it is not the case for Kiwi businesses.
The contract is with Australian company Computershare Investor Services Limited, which enlisted Sydney based Reach Investor Solutions to design and build the website.
Treasury was in charge of the tender process and says it needed a company with experience in online applications and the most qualified company won.
The State Owned Enterprises Minister is comfortable with it and notes the call centre and servers are based in New Zealand.
But the Greens say the Government should be fostering local talent.
"When people aren't watching, the Government is happy to give away these contracts to overseas companies and I think that it reflects the overall attitude of the Government - that they don't care if New Zealand goes into overseas ownership," Green Party co-leader Russel Norman said.
"We need to look at developing capacity in New Zealand because if we just let all of the skills and capacity go offshore, then all the profits will follow and we'll end up poorer for it."
The Co-Chair of NZRise, an organisation that promotes New Zealand digital technology businesses, said it should be a wake up call to local companies.
"We're certainly not against overseas companies winning contracts where they are tendered in an open and appropriate way," Don Christie told ONE News.
"If they come in with a better solution that's great, that means we have to lift our game."
He said overseas bidding is inevitable, but New Zealand firms can handle the big contracts.