A Nobel Prize-winning economist who advised Jeremy Corbyn is urging Sir Keir Starmer to ramp up public borrowing and turbocharge investment. Joseph Stiglitz, an economic guru of the political left, is calling on Labour to be more radical after “underpromising” in the run-up to the general election. The former World Bank chief economist told The Telegraph: “I think Labour needs a more aggressive public investment agenda. It is the same problem that we have had in the United States with under-investment in infrastructure.” It comes after Labour earlier this year dropped its £28bn green investment pledge, blaming high interest rates and the Government’s bid to “max out the credit card”. Sir Keir’s Opposition instead unveiled revised plans to spend under £5bn a year on environmental projects during its first Parliamentary term if elected, as the polls widely suggest. This has led to a warning by Mr Stiglitz, who also formerly advised former US presidents Bill Clinton and Barack Obama, that Britain risks “being left behind” if it fails to embrace net zero. He said: “Biden said he was going to be spending something like $350bn (£277bn) on the green transition. The current estimates are over $1tn. That is...