On Thursday, UBS said that property in all European cities now exceeds fair valuation, with London the most overvalued market on the continent and the city most at risk in the world for another housing bubble.
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"The UBS Global Real Estate Bubble Index, as well as the cross-sectional benchmarks, point to the risk of a substantial price correction should the fundamentals for real estate investment deteriorate," the bank warned in its global property report.
London house prices, in real terms, are 6 percent above their previous peak in 2007, with real estate in the capital decoupling both from the rest of the U.K. and local household earnings, according to UBS.
The city is the world's least affordable, bar Hong Kong, which UBS ranks as the second-most likely city to have a property bubble.
"Foreign demand (for London properties) and demand deriving from safe-haven seekers largely explain current valuations. Global geopolitical risk and the high property valuations in Asian cities have helped to propel London house prices to new heights," UBS said.
"Domestic buyers too have contributed to the appreciation," the bank added, highlighting the alluring yields on buy-to-let investments and ongoing population growth.
After London and Hong Kong, Sydney was singled out by UBS as the world's most overvalued city — a feature that has also been highlighted by RBS.
Alberto Gallo, head of European macro credit research at RBS, warned in a research note on Wednesday that Australian banks could be at risk from a house price correction, stating that mortgages accounted for over 60 percent of their loan portfolio (almost double the share in the U.S. and three-times the share in the U.K.)
Low interest rates have encouraged borrowing in Australia, with the debt-to-income ratios of households rising above those in the U.S. and the U.K. and house prices in Sydney overtaking London, according to Gallo.
Earlier this month, Deutsche Bank also warned of a boom in global property prices, driven by loose monetary policy across the world, with policymakers in Japan and Europe still contemplating further stimulus measures.
"Beyond the chatter about how impossibly expensive the likes of London and New York have become, the topic draws far less attention than it merits from policymakers and investors alike. That is unwise. Both economic theory and empirical evidence tell us that property prices are exactly where we should look for exuberance," said Deutsche Bank in a report.
Tokyo in Japan and Vancouver in Canada were also deigned overvalued by UBS. In addition, the prime minister of New Zealand discussed the issue of soaring house prices with CNBC on Friday.
"House prices doubled under the previous government and they've gone up pretty similar numbers under us," Prime Minister John Key told CNBC, speaking specifically about Auckland, the country's most populous city.
"The population's growing reasonably rapidly; there have been supply issues, so we're doing a lot of different things. We're building a lot of houses, so to give you an example, we've got the highest consent rates and building rates for a decade, but we're building three times as many houses as we did say seven years ago when I became PM."
US fair valued?However, UBS and Deutsche Bank judged real estate in U.S. cities to be mostly fair-valued, even in New York. San Francisco was singled out as an exception by UBS, with prices fueled by foreign demand and the fast-growing economy of Silicon Valley. Chicago, meanwhile, was judged to be undervalued relative to its own history.
"Even in the U.S., pockets of potentially lofty valuations are surfacing. Commercial real estate prices are now 13 percent above the pre-crisis peak, while the price of farmland has nearly doubled in real terms over the past decade," Deutsche Bank said.
Several emerging markets have also joined the rally, with residential real estate prices rising sharply in India, Turkey, Hungary, the Philippines and Thailand in the first three months of the year, according to the Bank for International Settlements (BIS).
However, these gains were dwarfed by the 17 percent increase posted by Ireland — a country hit hard when its property market collapsed in 2007.
Countries that proved exceptions to the rule include France, Greece and Italy, where real residential property prices mostly fell in the first quarter of 2015. Plus, China and Russia both posted sharp falls in prices, according to the BIS.