Sajid Javid’s suitability as chancellor of the exchequer has been called into question by his opposite number, John McDonnell, who has written a scathing letter to Boris Johnson demanding an investigation into Javid’s time at Deutsche Bank.

In the letter to the prime minister, dated July 31, the shadow chancellor called for Johnson to launch a probe into Javid’s nine-years at the German lender before he became a politician, focusing on his time as a banker in the run-up to the financial crisis.