A sixth prime minister in seven years — it was an unimaginable prospect not so long ago, but now, some experts are describing it as an inevitability facing Britain.Sir Keir Starmer, who led Labour to a landslide general election victory in July 2024, has become so unpopular that even some colleagues are framing his demise as a case of not if, but when.This week has been another shocker for the PM, who has been trying to explain how Peter Mandelson — a Labour kingmaker and friend of the child sex offender Jeffrey Epstein — ended up as the United Kingdom's ambassador to the US.Critics have been calling on Sir Keir to resign for months, but on Wednesday, Labour MP Jonathan Brash added his voice to the growing chorus.He used an interview on British television network GB News to rail about the PM's leadership, saying he was "fed up" with the "psychodrama in Westminster"."I mean, ultimately, we're in a situation now where I don't think anyone reasonably expects the prime minister to lead the party into the next election," he said.Mr Brash's time frame is generous He is often characterised as the architect of Mandelson's appointment.Not everyone believes the PM is doomed.Tom Baldwin, a former senior Labour advisor and Sir Keir's biographer, told the ABC that while the leader was under pressure, his fate was not sealed."These things turn around very, very fast and anyone making predictions in the current atmosphere is a fool