Pakistan, July 15 -- Andy Burnham was on Tuesday striding towards becoming the UK's next prime minister, winning the backing of the country's largest union, adding to an already unassailable lead in Labour's leadership contest.

The former Manchester mayor, so far the only candidate to be the party's new leader, had notched up 349 nominations from fellow MPs late on Monday - making it mathematically impossible for any challenger to defeat him.

The 56-year-old is bidding to replace Keir Starmer, who announced his resignation last month, bowing to months of internal pressure to step down after a series of scandals, missteps and policy U-turns in his two-year tenure.

The Unison trade union, the largest in Britain with more than 1.3 million...