Any mergers between Australia's major banks would not be prudent, the treasurer, Wayne Swan, told an industry conference yesterday.Speaking to the Bloomberg Australia Economic Summit, Swan said: "What isn't widely known is that there was growing pressure in the winter of 2008 to see an end to the four pillars policy." The Labor government reaffirmed this policy, which dates from the early 1990s, at the time."The four pillars policy has endured, in one form or another, through seven successive treasurerships over more than two decades and has served Australia well in all that time," Swan said. "Not only is it hugely important for banking competition, but it wouldn't be prudent to have the soundness of our banking system resting on the strength and risk management skills of three banks rather than four. "I think everything we've learned since 2008 about systemically important financial institutions shows this decision was the right one."