Chancellor of the Exchequer Alistair Darling has warned banks that they must either open up lending to businesses and mortgagees or face a competition inquiry.After a meeting with the chief executives of the UK's seven largest banks, Mr Darling warned that banks would not be able to use the Bank of England's historically low base rate to simply shore up their profit margins and reminded them of their obligations to ease credit flow for small and medium-sized businesses.The Times reports that the City minister Lord Myners would call each of the major banks to the Treasury to scrutinise their lending books and ascertain how much they have been charging mortgagees and businesses for credit."The Chancellor and I are not satisfied that lending is as it should be, even now after this time that we have been operating our policies," said business secretary Lord Mandelson, who was also in attendance at the meeting.Earlier this month, the chancellor also reiterated the Treasury and the Financial Services Authority's commitment to ensuring that banks do not overextend themselves with untenable gearing ratios and lax lending strategies.