The Reserve Bank of New Zealand has signalled it is accelerating plans to bring in a third round of controls on high loan-to-valuation ratio lending on rental property investors before the end of this year.The move followed the central bank's decision on Thursday to hold its Official Cash Rate at 2.25 per cent, which surprised some economists and those in financial markets who had priced in a 25 per cent chance of a cut to two per cent.RBNZ governor Graeme Wheeler cited double-digit house price inflation in Auckland that is spreading to other major cities as a factor in his decision not to cut. Wheeler said the risks to financial stability of an over-valued Auckland property market meant the bank was actively discussing with Finance Minister Bill English the potential to introduce a third round of LVR controls before the end of the year, and potentially introduce British and Irish-style limits on debt-to-income multiples.Wheeler told a news conference for the bank's June quarter Monetary Policy Statement that discussions had already begun on both a new set of LVR controls that were likely to target investors who were now responsible for 40 per cent of property purchases around New Zealand and 46 per cent in Auckland."We've had discussions with the Finance Minister on macro-prudential tools. We've talked to the Finance Minister and said that we're doing some work on loan-to-valuation ratios, which the market is familiar with, and that we also wanted to do some work on debt-to-income ratios. We also said that that latter work is likely to take longer," Wheeler said."But we'll be probably talking with the Finance Minister in the next few weeks in terms of the consultative process that we go through," he said.Asked if the Reserve Bank would have new controls in place before the end of this year, he said: "It's possible that we would be moving before the end of the year, or before that."Wheeler said the Reserve Bank viewed the LVR controls as very successful because they had reduced the amount of highly leveraged lending by around NZ$20 billion and had reduced the share of highly leveraged mortgage lending from 21 per cent before the first round of controls in November 2013 to 13 per cent currently. The Reserve Bank introduced a second round of controls in November last year that targeted Auckland rental property investors by limiting their borrowing to 70 per cent of the value of a property. Other borrowers are limited to 80 per cent."That's why we're also now in this situation looking at LVRs and saying 'is there anything else we might need to do?' - particularly given the rapid growth in the volume of transactions that are related to investment properties," he said.Asked if the Reserve Bank was looking at increasing its deposit requirement for Auckland investors from the current 30 per cent, Wheeler said: "It's just one of the scenarios that we're looking at. We haven't made any decisions on that.""We're doing quite a lot of analysis