The row raging in Canada over white and yellow butter took a new twist this week.

Canola growers and oilseed processors asked the four provinces that make up western Canada to ban the import of yellow butter from Quebec in retaliation against regulations in Quebec that stipulate that margarine must be white.

The canola industry claims Quebec has failed to honour a pledge to get involved in a an investigation into its ban on yellow margarine, which is coloured to resemble butter, reports the Winnipeg Free Press.

“We’re asking the western provinces to restrict Quebec butter coming into Western Canada to be white, as our margarine must be going into Quebec,” said Ross Ravelli, president of the Canadian Canola Growers Association.

Quebec is the only Canadian province that forces margarine producers to make their products look different from butter. The measure is intended to protect the province’s huge dairy industry.

Earlier this year the Canadian subsidiary of Anglo-Dutch consumer goods giant Unilever argued in court that the Quebec ruling costs it C$1m (US$) every year. That case is still unsettled.