They showed that Prime Minister Bill English, while Finance Minister, and Steven Joyce, while Economic Development Minister, favoured SEZs.
The zones are also backed by Local Government New Zealand, the New Zealand Initiative thinktank and some district councils.
"If this went ahead, anywhere the Government wanted to carry out development - they could," Hague said.
"Roading through National Parks, irrigation dams, energy generation, aquaculture, controversial tourism developments - you name it."
Another region that had been considered for a SEZ was Southland, where aquaculture development was being investigated at one Stewart Island site described by a briefing paper as containing "some of the largest areas of near pristine marine habitat in New Zealand, with significant natural heritage values".
Other work discussed in the OIA documents was a "single window" for all necessary approvals for mining developments on the West Coast.
"The Government is seeking to give themselves the powers to push through controversial and damaging projects that would otherwise fail because they breach environmental limits."
Bridges this afternoon rejected the claims.
"They are trying to paint this in a very simplistic and therefore misleading way as a bulldozer to the current laws - it is not that."
Work around SEZs were part of the Government's wider Regional Growth Programme and the measures had been called for by many groups, he said.
But they were still only a matter for consideration, with officials advising ministers of the complexity and issues involved.
"They are not easy to do and the cons may outweigh the pros," he said.
"We are certainly not saying it's now off the table - we need to discuss it and we know it's an important issue for a number of parties, but I don't think we are going to be coming out with a particular special economic zone policy any time very soon.
"In relation to mining specifically on the West Coast, it's important to say that is a sector that has been the lifeblood, the mainstay, of that region for a very long time, with many jobs and in fact some of the highest paying jobs in the economy.
"But we also understand that there are very deep-seated conservation views and values at play which make it a fraught and complex issue."
Bridges also disagreed with assertions the work had been done in secret.
"It's a workstream - just because we don't shout it from the rooftops, because we haven't reached a final position, doesn't mean it's secret."
