The LIBOR scandal is one of the greatest outrages we have seen in financial services, and I was so disappointed with the way Bob Diamond – until recently Group Chief Executive of Barclays plc – conducted himself before the Treasury Select Committee last week.

As we have all been discovering in the past few weeks, the breadth of the scandal is startling, with dozens of banks in countries around the world colluding with each other for years to fix the London Interbank Offered Rate (LIBOR), the rate of interest used in lending between banks and as a reference in setting the interest rate on all sorts of other loans. LIBOR influences the price of literally trillions of pounds of financial transactions every year.

Barclays has just been fined £290m for its role in trying to fix the LIBOR from at least as early as 2005, and it is likely that more fines for more institutions will follow in the coming weeks and months. The Financial Services Authority and Serious Fraud Office have made clear in their investigations that traders from the bank have lied about what it was costing Barclays to borrow from other banks, with emails between traders and rate submitters showing the levels of collusion in trying to influence the LIBOR to boost personal profits as well as to hide the liquidity problems banks were facing.

The depth of the impact on consumers and the wider banking sector may never be uncovered, but many mortgages – especially buy-to-let mortgages – are directly linked to LIBOR, and lenders will also have used LIBOR to decide whether to make other loans or credit card deals more expensive or cheaper.

As someone with a 25-year career in the banking and finance industry, including with Barclays Group from 1987 to 1997, I am well aware of the procedures and safeguards that should have caught those involved in the LIBOR scandal much sooner, or prevented it from happening in the first place.

This is why, when I had the opportunity to question Mr Diamond as a member of the Treasury Select Committee last Wednesday, I was appalled by the superficial nature of his answers, and his apparent disregard for the extent of the problem.

As I said to Oliver Wright of the Independent, previously the issue with banks had been about arrogance and greed in the run up to the financial crisis, but the LIBOR scandal demonstrated blatant criminality, encouraged by an attitude within banks that traders could be remunerated vast sums for the profitability of their own book, regardless of what that did to the bank, to other banks, or indeed to consumers.

I would encourage you to read the whole transcript of Mr Diamond’s appearance before the TSC, and you can find my contributions on pages 23 through 29. Alternatively, you can watch my remarks in the session below.