Montreal mayor Denis Coderre held nothing back in slamming Ottawa's last-minute decision to stop Montreal from dumping sewage.

"It's irresponsible, it's unjustified and it's against Montrealers," said Coderre.

His comments come after the federal government demanded on Wednesday that Montreal cease its plan to dump sewage into the St. Lawrence river beginning on Sunday.

Intergovernmental Affairs Minister Denis Lebel said that Environment Canada wants to have an independent review of Montreal's plan.

"The St. Lawrence River is one of Canada's most important waterways," said Lebel.

Coderre said that was ludicrous, as Environment Canada has been sitting on documents for more than a year, and has everything it needs to proceed with an analysis of the plan.

"Somebody's playing politics, it's not the bureaucrats, it's not the officials and it's clearly not me," said Coderre. 

Holding a stack of papers sent to him by ministry officials, Coderre added "I have the e-mail here and he's saying clearly that I have all the information that I need, there's no problem, we can make all the analysis to take the decision."

He added that he has no plans to disobey the order but that delaying the maintenance work on the waste water collector past Oct. 23 could put the river at greater risk.

It would also delay the reconstruction of the Bonaventure Expressway.

Montreal came up with plans more than a year ago to temporarily divert untreated wastewater into the river for about a week while a snowmelt collector is replaced.

Quebec's Environment Ministry approved the plan, saying its analysis of the plan showed there was no other alternative to flushing 8 billion litres of wastewater into the river.

Nobody from the federal ministry made any comments about Montreal's plan until this month, with Federal Environment Minister Leona Aglukkaq saying she had never heard of the plan.

On Tuesday an activist presented Coderre with a 90,000-signature petition against the planned dumping, but Coderre said as much as people dislike the plan, the city had no choice but to continue. 

Experts say there will be an effect to the environment from the plan, but Montreal said it has done everything it can to minimize the impact.