The Environment Ministry's own officials struggled to explain the government's proposed water standards to the public, emails reveal.
Emails released under the Official Information Act reveal officials at the Environment Ministry were also having trouble with the technicalities.
The day after the policy was announced, a ministry staff member emailed scientists at NIWA and in the United States, asking for "any thoughts or suggestions".
"We are struggling to explain the science in easy to understand terms for the general public," the email said.
Green Party co-leader James Shaw said it was "embarrassing" for Environment Minister Nick Smith.
"He went out so publicly with an announcement that his own officials struggled to be able to communicate."
Labour water spokesperson David Parker said the policy was "incomprehensible" and an indictment on the government.
"If the ministry can't explain it in a way that the public can understand, how can they expect the public to have confidence that they're truly going to get swimmable waters?"