The Australian Taxation Office is the fastest-growing lender in Australia, thanks to a culture - or is it policy? - that allows tax debts to go uncollected for ages.Forget trends in private sector lending as a measure of credit stress.On-demand, unsecured, unexamined loans are readily available from the Australian Taxation Office, which makes little effort to collect small, unpaid business and personal tax debts.ATO Bank arrears can easily exceed 365 days and a debt over by two years or more may not matter much: at least not to the point where'd you'd refinance in the private market. The ATO simply don't ask hard, but just capitalise interest and readily enter into payments plans; repeatedly so.Overall credit growth is 15 per cent and business credit growth is 19 per cent, according to the RBA, and the ATO's growth rate as a lender has to be higher - and probably quite a lot higher.The recent growth of ATO tax debts is something that can only be guessed at, since Tax publishes data slowly.The last estimate, a year old now, was small business tax debts of $8 million, up 35 per cent in the three years to June 2006.As an established lender of last resort the ATO seems an obvious avenue for capital for businesses feeling the effect of earlier rises in interest rates and those funding their June top up in tax-free retirement savings.So whatever the pattern of rising delinquencies apparent within the banking industry (and we'll be hearing more on that starting with Adelaide Bank tomorrow) you can be sure this is magnified in the case of the ATO. The architects of this lending by the ATO are Peter Costello, treasurer; Ken Henry, treasury secretary; Michael DíAscenzo, tax commissioner and Glenn Stevens, Reserve Bank governor.The ATO's lackadaisical approach to the pursuit of its debts underlines a broader truth: money is easy, credit still seems cheap and almost all relish the stimulus that a prolonged credit boom confers.As custodians of a fast growing debt portfolio Australia's econocrats know better than any banker that demand for credit is accelerating and that credit quality is declining.And their view of this?Well, one way we'll know is courtesy of the RBA's interest rate announcement scheduled for 9.30 this morning.A stable interest rate would suggest John Howard, prime minister, is calling the shots on economic policy, and a stable rate is the better outcome.Howard probably knows that APRA and the lenders mortgage insurance companies are making some effort to engineer a credit crunch, of sorts, and that lenders will start to feel the heat of this shift soon.All LMIs have to have more capital than before, most offshore LMI substitutes have to submit to APRA scrutiny and - handily - the US owners of Genworth and PMI are reducing their appetite for Australian credit risk. This latter position is dictated by the contagion in US mortgage markets from America's own culture of easy credit.The planned entry of MGIC, which took over Radian (and which had designs of