The paper discusses the effects on growth of a systemic banking crisis as a result of debt defaults. These effects will come from the impact of credit rationing on consumption and credit and from the impacts of a significant rise in the spread between lending and borrowing rates for both producers and consumers. The analysis uses the dynamic stochastic general equilibrium version of the National Institute global model. The paper also investigates the impact on output of a permanent, regulation induced, rise in margins in the financial sector, taking into account the impacts of regulation on equity market valuations.