Hutt City Mayor Ray Wallace told a parliamentary select committee yesterday that these limits did not give communities a chance to respond.
"In this case the commission has time on its side to develop a proposal but the community ... is constrained ... by that very tight timeframe."
A petition for a vote on a merger of councils in the Wellington region would need about 48,000 signatures.
Napier City Council Mayor Barbara Arnott said "it would not be physically possible" to collect a tenth of a region's signatures in the short time proposed.
Most councils wanted a poll to be compulsory for any merger and for a vote to be held in each affected area.
Under the planned reforms, a vote on a merger needed a majority of support from the entire affected population, instead of in each territory.
The bill before the committee would refocus councils on "core business" to cut rates rises.
Mr Wallace was concerned that if Hutt City Council was merged into a super-council, residents would have to absorb the higher rates of neighbours who had spent more on infrastructure.
His council had the second lowest average rates increase in the country, after the Chatham Islands.
Prime Minister John Key has told councils they will not be forced to merge, and communities would be able to debate proposed mergers.
The Local Government Commission would have to be convinced a merger had significant community support before it recommended the formation of a super-council.
Fifteen councils submitted to the committee yesterday, unanimously challenging the grounds for the bill.
The Government introduced the reforms because it felt councils' spending on non-core business had led to a rates blowout.
Change in merger rules
Now
* Mergers can be proposed by a local body, minister, or petition signed by 10 per cent of ratepayers.
* A majority of residents must approve it in each area.
Proposed
* Any person or group can propose a merger.
* If a merger is approved, it can be blocked only by a petition signed by 10 per cent of the affected population within 40 days.
* A majority of those affected must then vote for it to go ahead.