The Reserve Bank of New Zealand has signaled it is considering introducing British style debt-to-income ratio limits to further slow mortgage lending growth in a housing market that is taking off again.The RBNZ introduced loan-to-valuation ratio limits in 2013, restricting mortgages with LVRs above 80 per cent to ten per cent of new lending.The RBNZ published its half-yearly Financial Stability Report yesterday, including a warning about resurgent house price inflation in Auckland that is now also spreading elsewhere in both the North and South Islands. It said it was assessing whether "further financial policy measures were appropriate." But RBNZ governor Graeme Wheeler and deputy governor Grant Spencer were much more direct in their comments in the news conference that followed the release of the report.They said they were "increasingly concerned" about the Auckland housing market and were "seriously considering" introducing new lending control measures, including a new debt-to-income ratio control.The Bank of England limited loans with a multiple of more than 4.5 times income to no more than 15 per cent of mortgage flow from October 1, 2014. Currently around 35 per cent of owner-occupier mortgage lending in New Zealand is done with debt-to-income multiples of more than five, while almost 60 per cent of investor lending is done with DTIs of more than five.Wheeler and Spencer did not put timeframes on when the new controls could be introduced, but said the bank was actively analysing the issues and looking at whether to renegotiate the bank's memorandum of understanding on its macro-prudential tool kit with Finance Minister Bill English."I think it is fair to say we are becoming increasingly concerned about the Auckland housing market," Wheeler said."House price inflation looks like it has accelerated in February and March. We hope to see the REINZ data this afternoon and investor activity is driving a lot of that market," he said.The Real Estate Institute of New Zealand released data later yesterday showing New Zealand's annual house price inflation rate rose to 14.5 per cent in April from 13.3 per cent in March. "So will we look at further macro-prudential? Yes, we are," Wheeler said."We need to do more analysis. We need to have discussions with the Finance Minister, but it's fair to say that we're seriously looking at macro-prudential," he said.Specifically asked about debt-to-income ratios, he said: "It is something we would look at. It has been successful in other countries, particularly the UK, which has recently adopted debt-to-income ratios."Prime Minister John Key and Finance Minister Bill English said they were open to a potential RBNZ proposal to limit debt-to-income ratios, which would require the agreement of English in an expanded memorandum of understanding for macro-prudential policy.Key told reporters in Parliament when asked about the possible RBNZ measures that the Government did not want to see a bubble emerging in the housing market."And potentially if there are recommendations, the government is not ruling out adopting those recommendations or allowing the Reserve Bank to do it," Key said."We've already done that before with