Amicus and the Transport and General Workers Union (T&G), which are due to merge next month, have signed an accord in Canadian capital Ottawa to set up a “merger exploration committee” with the North American United Steel Workers (USW).

The accord was signed at the USW’s Canadian conference. The USW covers both Canada and the US.

No timeframe has been put on the talks. However, if they are successful, they would result in a union of 3.4m members across the UK, Ireland, Canada and the US.

Amicus general secretary Derek Simpson said the potential merger was a response to the growth of multinational companies that “are pushing down wages and conditions for workers… by playing one national workforce off against another”.

Tony Woodley, general secretary of the T&G, added: “This is a historic step for global trade unionism.”