Photo: The Canadian Press

TORONTO — Experts warn that a post-Brexit United Kingdom will present Canadian business with tremendous uncertainty about billions of dollars worth of trade and investments, no matter how the British Parliament votes on Saturday.

The outcome of the unusual weekend vote in London is itself far from predictable, as British Prime Minister Boris Johnson struggles to get support for a controversial agreement that he reached Thursday with the European Union.

But observers say even a Johnson success would only provide a starting point for further rounds of difficult negotiations between London and Brussels and eventually between Canada and the United Kingdom.

Fasken partner Clifford Sosnow says the primary benefit of Johnson’s plan is that it would provide for 14 months to 36 months of negotiations on a new trade deal for two of Canada’s biggest export and investment markets.

“The major concern for everybody is the instability and the instability from not knowing what the business relationship will be, what the investment relationship will be,” says Sosnow, who provides strategic advice about international trade and investments at one of Canada’s largest business law firms.

He adds that open talks between the United Kingdom and Canada would be allowed only after the U.K. leaves the European Union on Oct. 31, if Johnson’s schedule is passed by the British House of Commons.

The United Kingdom by itself, represents one of Canada’s top five destinations for investments and top 10 markets for goods and services.

It has also been a gateway for Canadian companies that do business in the European Union, which is Canada’s second- or third-biggest trading partner after the United States and China, depending on the measure.

About 40 per cent of Canadian trade in merchandise with the EU goes through United Kingdom, says Achim Hurrelmann, a political scientist and co-director of Carleton University’s Centre for European Studies in Ottawa.