Canadian Prime Minister Justin Trudeau and his wife Sophie are separating and have signed a legal agreement, his office says in a statement that appears to mark the end of the couple’s 18-year marriage.

“They have worked to ensure that all legal and ethical steps with regards to their decision to separate have been taken, and will continue to do so moving forward,” it said.

The two said in statements posted on Instagram on Thursday (AEST) that they made the decision after “many meaningful and difficult conversations”.

Mr Trudeau, 51, and Sophie, 48, were married in late May 2005.

They have three children.

“They remain a close family and Sophie and the Prime Minister are focused on raising their kids in a safe, loving and collaborative environment,” the statement said.

“The family will be together on vacation, beginning next week.”

Mr Trudeau is the second prime minister to announce a separation while in office.

His father Pierre Trudeau separated from wife Margaret in 1979. The two divorced in 1984.

Justin Trudeau channelled the star power of his Liberal icon father when he first won office in 2015.

Scandals, voter fatigue and economic inflation have taken a toll on his popularity after eight years in power.