The Green Party is set to shift its politics leftwards under new leader Zack Polanski, after he won a landslide victory in the party’s leadership contest.Mr Polanski, who spoke of wanting to shift the party’s politics towards “eco-populism” during the leadership race, could offer a fresh headache to Sir Keir Starmer’s Government from the political left.The new Green leader warned “we are here to replace you” in a message to the party of Government, during his victory speech.