The City watchdog has turned to American regulators and bankers for advice as part of its probe into the controversial car financing industry to assess whether there has been a “structural” shift in the way Britons buy vehicles.

An explosion in a new type of car loans called personal contract purchases (PCPs) has helped to fuel the recent rapid growth in consumer credit, a lending boom that has drawn scrutiny from the Bank of England and the Financial Conduct Authority (FCA) amid concerns it could be a bubble.

Earlier this week, the Bank estimated that car finance has increased at an average annual rate of 20pc since 2012, equating to a £30bn rise in total stock. Some City analysts have speculated that if the valuations underpinning car loans are wrong, it would set the industry up for a crash.

The FCA revealed earlier this year that it was assessing the motor finance industry because it was “concerned that there may be a lack of transparency, potential conflicts of interest and irresponsible lending”.

Andrew Bailey, the chief executive of the FCA, disclosed today that the “starting point” for the inquiry was “has there been a structural change in car finance in this country?”