At the time Burnham proposed this extra £40 billion of borrowing, the government was running a deficit of nearly £140 billion a year.

One analyst said markets would reprice U.K. fiscal risk "accordingly and quickly" if Burnham's political ambitions come to light.

The Greater Manchester mayor appears set to challenge for the Labour leadership

At the time Burnham proposed this extra £40 billion of borrowing, the government was running a deficit of nearly £140 billion a year.