MONTREAL -- The City of Beaconsfield, in Montreal's West Island, says it will pay its 2020 agglomeration contributions under duress for the first time.

This comes after Beaconsfield Mayor Georges Bourelle revealed last December that his council was evaluating legal options to sue the City of Montreal and recover what it calls “overpayments of $12 million annually.”

"This is the first time that a payment is made under protest. The unfair and inequitable treatment of our residents must stop," he said. "Montreal turns a deaf ear to our claims because it benefits financially from the present situation and has the sole decisive power despite the serious prejudice to our tax payers."

Bourelle, who is also vice-president of the agglomeration’s Standing Committee on Finance and Administration, calls the alleged overpayments "injustices," claiming city officials are using a complicated mathematical formula to hide surtaxes.

According to Beaconsfield officials, the formula is based on property evaluation, fiscal potential and the breakdown of residential, institutional, commercial and industrial tax bases.

For a couple that owns a home, Beaconsfield states overpayments represent $1,200 in surtaxes; for a family of four, that amount jumps to $2,400.

"This injustice is driven by the distorted system and Montreal's lack of political will to address the issue. This can't keep going on," Bourelle argued.

Last December, Montreal Mayor Valérie Plante refuted Bourelle's argument, saying "where Beaconsfield or other cities might pay more, they pay less as well on other things."

"I would ask the mayor of Beaconsfield to look at the big picture and not only to target a few elements," she said.

The City of Montreal has yet to respond to CTV News' request for comment on Beaconsfield's decision to pay its contributions under protest.