Mayor of Greater Manchester Andy Burnham. Leon Neal | Getty Images News | Getty Images Andy Burnham, the frontrunner to overthrow U.K. Prime Minister Keir Starmer, abruptly cancelled a call aimed at placating investors nervous about his potential policy mix on Monday, the FT reported. Burnham — who is not yet a sitting member of the U.K. parliament — will run in the June 18 by-election in Makerfield, north-west England. If he wins the seat, he is widely expected to launch a formal challenge to usurp Starmer’s position. Starmer’s premiership has been under intense pressure following a crushing defeat for the ruling Labour Party in the U.K.’s local elections. Political instability and Burnham’s bid to return to Westminster has sent jitters through the U.K.’s government bond market in recent weeks, amid expectations that he would be a tack to the left from Starmer and ramp up borrowing. The U.K. has the highest borrowing costs in the G7, with yields on its long-term gilts trading well above the critical 5% threshold. d’ title=”Interactive or visual content” class=”flourish-embed-iframe” frameborder=”0″ scrolling=’no’ style=”width:100%;height:600px;” …