Green MP Catherine Delahunty believes it is touch and go whether she can push stricter river protection legislation over the line.
Ms Delahunty is sponsoring a bill to cut the number of years companies can discharge waste into rivers without re-applying for permission, reducing the timeframe from 35 years to five years.
National and Act have always opposed the bill, so she'll need unqualified backing from all other parties to get it through its second reading, due in Parliament on Wednesday.
She acknowledges, however, that there is no guaranteed support for the second reading from Labour, New Zealand First, United Future or independent MP Brendan Horan.
