British Prime Minister Keir Starmer is facing a revolt within his own party — following political turmoil over his falling popularity that could result in the UK seeing its fifth leader in just seven years. Starmer, 63, whose Labor Party suffered major losses in last week’s local and regional elections, has seen his allies turn against him and call for his resignation to allow a new successor to rescue the ailing party. So far, however, no successor is openly challenging him — and so he has refused calls to resign. Should Starmer succumb to the opposition from ally and foe alike, his name would go on a growing list of unpopular PMs who were quickly ousted from leadership of the world’s fifth largest economy. Former PM David Cameron , who served from 2010 to 2016, is so far the only leader in the last decade who has served longer than three years. Keir Starmer is facing renewed calls to resign in the latest shakeup in British politics.…