Mark Cameron, who was director of global public policy at beleaguered Blackberry, has shifted to Hill+Knowlton Strategies as deputy leader of its Canadian energy practice. He’s a former aide to Canada’s prime minister Stephen Harper.

He is the latest in the exodus of executives at struggling Blackberry. t He follows COO Kristian Tear, CFO Brian Bidulka and CMO Frank Boulben who left the smartphone company last month.

Rick Costanzo, chief of sales, and Chris Wormald, head of mergers and acquisitions, are leaving by the end of the month.

Blackberry, which is based in Waterloo, Ont., is cutting 40 percent of its workforce in the aftermath of a collapsed takeover bid.

Interim CEO John Chen told staffers in a town hall meeting last month that “things are going to get worse before they get better.”