Nelson MP Nick Smith says it is too hard for local councils to merge and the law needs to change.
A proposal to merge of Nelson and Tasman has failed to get the 50% support needed in each area.
Preliminary referendum results issued on Saturday showed some 57% of voters in Nelson City supported the amalgamation, but 74% in Tasman were against it.
Dr Smith says the local government reform law is bureaucratic, drawn out and has a high threshold for change.
He says almost every attempt by councils to merge has failed.
Dr Smith also thinks the referendum result will be challenged, as he says Tasman District Council broke the law by using ratepayers' money to produce a pamphlet critical of the merger.
