A medical specialist is worried he may have lost important patient information after being inadvertently caught up in a Greenpeace-organised email campaign targeting Hawke's Bay Regional Council.

Napier-based anaesthetist Roger Scott said several thousand form emails - calling on the council to shelve its controversial Ruataniwha dam development - had "poured through the computer non-stop" on Tuesday and Wednesday.

"You just can't stop them."

He was worried the "spam attack" would result in him not receiving vital clinical information such as patient blood test results because they would "get lost in all this junk that keeps pouring through".

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Scott has been on the receiving end of the emails because he shares a home computer with his wife, Hawke's Bay regional councillor Christine Scott. The couple have separate email addresses but both their emails are downloaded through one email programme.

Greenpeace had emailed its database encouraging supporters to email Hawke's Bay regional councillors voicing their opposition to the dam, which will be part-funded by ratepayers.

At a council meeting on Wednesday, some councillors expressed their anger at being swamped with the emails, although one, Rex Graham, said there was an easy process to keep them out of the recipients inbox, which he had put in place.

Graham said such emails were a part of the democratic process but councillor Alan Dick said he had wasted considerable time deleting the emails and councillor Debbie Hewitt labelled them an "invasion".

After the meeting Regional Council Chairman Fenton Wilson said while the email campaign may amount to "some people's version of democracy," he believed it was "reckless and frivolous".

Scott emailed Greenpeace on Wednesday, demanding the emails stop.

"If the attack persists I will hold you responsible for any morbidity accruing to my patients," he told the organisation.

Greenpeace spokeswoman Genevieve Toop said the organisation had "encouraged our supporters to raise their concerns" about the dam with the council in the wake of the Havelock North gastro bug outbreak.

"Right now we've got a region that is suffering because of poor water quality and in that same region there is a proposal for a dam that is going to mean more industrial dairy farming and more water contamination so thousands of New Zealanders have called on plans for that dam to be scrapped."

Toop said the campaign was not a spam attack because it was "emails from individual New Zealanders who were very concerned about the situation in Hawke's Bay and the future ramifications of the dam".

Greenpeace had taken Christine Scott's email address from the council's website and "as a regional councillor she should be aware that she is going to get emails from concerned people about issues that she is making decisions on".

While the link between the couple's emails was "concerning," Greenpeace had removed the address "so that doesn't cause any more problems for him," Toop said.

However she stood by the intent of the campaign, which had seen almost 4000 people email the councillors by Wednesday morning.

"We should be cleaning up and protecting our rivers and water supplies, not building giant irrigation schemes that will further pollute them," she said.

"Councillor Scott is a democratically elected representative making decisions about the Ruataniwha dam which are of concern to people right around New Zealand. Those people have every right to raise their concerns with elected officials over email."

Roger Scott said he "couldn't agree more" with Greenpeace's democratic right to raise their concerns but said some of the emails "were from people who had no idea they were being cynically used by your organisation for its own political ends".