By David Milliken
MANCHESTER (Reuters) - The European Central Bank must be critical of market expectations for its future policy moves, basing its decision on economic data rather than financial market prices, ECB Vice President Luis de Guindos said on Tuesday.
The ECB has all but promised a stimulus package for its Sept. 12 policy meeting and market expectations have been growing. Investors are already pricing in several rate cuts for the coming year and a fresh round of bond purchases, commonly known as quantitative easing.
"Our monetary policy is data-dependent, not market- dependent: indications from market expectations cannot replace our policy judgment," de Guindos told a conference in Manchester.
"Another way of robustifying our analysis is to look for expectations beyond those expressed in financial market prices," he added.
Still, de Guindos was clear that record-low interest rates would stay low for even longer.
"I think that we have to act not ... aggressively but with a lot of determination," de Guindos said when he was asked about the prospects for negative interest rates. "The point is very, very, very, very clear: we are going to have low rates for longer."
The ECB's deposit rate, its key gauge, now stands at minus 0.4% and markets see it falling below minus 0.7% within a year.
But de Guindos also appeared keen to soothe expectations, noting the risk of the "echo chamber effect", when its strong signals start to get reflected in asset prices and markets no longer respond to news about the economy, as they are cemented by central bank communication.
"The echo chamber effect and the inherent noisiness of market signals are reasons why we need to take the expectations that are priced in financial markets with a pinch of salt," de Guindos said.
"The more forward guidance we give, the less informative are market signals for gauging the state and the expected evolution of the economy," he said.
The ECB has a solid record in guiding market expectations, but its stimulus measure have exceeded expectations at key points in the past, earning the bank a reputation for being able to surprise.
(Writing by Balazs Koranyi; Editing by Andrew Heavens, Larry King and Frances Kerry)