Reserve Bank of Australia governor Glenn Stevens has given his clearest signal yet that the RBA will "lean" against future asset price bubbles under the right circumstances.The RBA has cautiously favoured using monetary policy and other tools to lean against asset price bubbles for several years. In 2010, it argued that it had successfully leaned against Australia's house price boom in 2002-2004.And in a transcript of his remarks to an August RBA conference, released yesterday, Stevens appeared even more convinced monetary policy should be used against bubbles. He said financial stability and monetary policy were related, although the relationship was complex.The conference brought together RBA staff, other central bankers and outside economists to discuss the relationship between property markets and financial stability.Stevens emphatically rejected former US Federal Reserve chairman Alan Greenspan's alternative approach of "cleaning up the mess" after an asset price bubble.Stevens appeared to be influenced by the protracted period of slow growth in Europe and the US. He said that "by this point we have to conclude that simply expecting to clean up after the credit boom is not sufficient anymore.""The mess might be so large that monetary policy ends up not being able to do the job when the time comes. Moreover, if the monetary policy clean-up after the asset price bust involves interest rates low enough to prompt some other sector of the economy to leverage up in order to spur the growth, then the clean-up itself might leave its own toxic consequences."The debate has moved, it seems to me, some way towards doing a bit more leaning."Stevens also continued a common theme of Australian regulators in recent months by arguing that active prudential supervision was essential to minimising the impact of financial collapses and crises. Monetary policy could not manage cycles, asset values and leverage all by itself, he said.