Coffey said the short two-week submission period was because the council wanted to have the law passed by June so it could put in place the change in time for this year's local body elections.
However, he said it was far from certain it would pass in time given the demands on Parliament. The due date for the committee to report back is in October, but he was still hopeful of getting it back to Parliament earlier.
Coffey said he accepted there was concern that it was being rushed and about the proposed changes. "By extending the submission window we are hoping people who think it is a rushed process will be able to get the opportunity to have their say as well."
He said there was similar opposition to an earlier law change to Māori wards, which removed the provision for the outcome of a local referendum to block the creation of Māori wards.
National's justice spokesman Paul Goldsmith said the initial two-week submission period was "outrageously short".
The Government was trying to "sneak through" the bill, despite it being a significant change to electoral laws.
"Bringing through constitutional change in an obscure local bill is not the way to do things."
He said the effect of moving away from the population-based criteria for Māori wards would effectively change the principle of each vote being equal.
Although the bill was restricted to the Rotorua district council, it would open the door for other councils to follow suit.
"So [Labour] are just sneaking it through and it will then be presented as a fait accompli."
The extension to submissions will also allow more time for the usual Attorney-General report on the bill's implications before MPs have to vote on it again.
About 1400 submissions had already been received. Oral submissions will start to be heard from Friday, despite the extension to the time frame, and the committee will split into two groups to allow more to heard quickly.