OTTAWA -- Here are five things to know about Thursday's British referendum on its future in the European Union, the official Canadian position and the potential economic consequences of a vote to leave:

1. Prime Minister Justin Trudeau, Foreign Affairs Minister Stephane Dion, Finance Minister Bill Morneau and former Conservative prime minister Brian Mulroney have all spoken out in favour of Britain remaining in the EU.

2. Trudeau says Britain has been a strong partner for Canada in the EU on the Comprehensive Economic and Trade Agreement, and would help to drive the free trade deal to ratification by next year if it remains at the EU table.

3. Were the 'Leave' side to win, it would trigger an article in the European Union treaty that has never been used, but would require a long period of negotiation -- years, perhaps -- between the EU and Britain on the terms of departure.

4. During this negotiation period, Britain would still be subject to all EU treaties and agreements, which would including the Canada-EU trade deal. But Canada's High Commissioner to Britain, Gordon Campbell, has questioned whether the EU would have the ability to follow through and ratify the deal if it was also faced with negotiating Britain's exit.

5. One Canadian politician, former House of Commons Speaker Andrew Scheer, is swimming against the anti-Brexit tide. The Conservative MP argued in a column in the National Post newspaper that Britain would thrive outside the EU and its relations with Canada would prosper -- a position that has him at odds with many world leaders and financial institutions.