The Federal Housing Administration, the government agency that insured $360bn of US single-family mortgages last year, said on Thursday that its insurance reserves had fallen below its congressionally mandated threshold to their lowest level ever.

Amid depressed house prices and mounting losses on insured mortgages, the FHA’s capital reserve ratio, which measures reserves after accounting for projected losses, fell to 0.53 per cent in the 12 months to September 30 – well below the 2 per cent cushion it is required by Congress to maintain.