UPDATE 1-ECB Noyer:Need accounting change once crisis passed

(Updates headline)

By James Mackenzie

WASHINGTON, Oct 12 (Reuters) - Accounting rules used to set a value on the assets held by banks need to be overhauled but it would be wrong to move during the financial crisis, European Central Bank governing council member Christian Noyer said.

How to put a value on the complex array of structured credit products owned by banks has been one of the key issues at the heart of the turmoil sweeping global financial markets and there have been widespread calls for an overhaul of the rules.

But in a paper published in the Bank of France's Financial Stability Review for October on Sunday, Noyer, who is also Governor of the Bank of France and head of the French Banking Commission, cautioned against rushing to issue new regulations.

"Noting that valuation rules may not be optimal for all instruments in all market circumstances does not mean that they should be changed in the midst of a crisis," he wrote.

Leaders of euro zone countries, who were holding an emergency meeting on Sunday to discuss pan-European measures aimed at propping up the battered financial sector, also cited the need to consider current conditions in changing accounting rules.

A draft statement of the leaders' meeting mentioned ensuring sufficient flexibility in the implementation of accounting rules given current exceptional market circumstances.

A sudden change of the rules as markets have been collapsing could raise moral hazard issues and amount to "valuation forbearance" -- allowing companies to gloss over losses on their portfolios, the paper said.

Noyer said accounting rules "should be structured so as to support best risk management and disclosure practices in both upturns and downturns."

Since the collapse of Lehman Brothers last month, uncertainty about whether a bank may be sitting on toxic investments that could leave it exposed to fatal losses has made financial institutions fearful of lending to each other.

As a result the vital system of interbank lending that keeps the financial system running has all but frozen.

"In many respects the current crisis is about valuation," Noyer noted.

WEAKNESSES

His paper said the crisis had laid bare a series of weaknesses relating to the way different accounting systems set a value on assets in bank balance sheets and thus allow the market to form a picture of a risk of default.

There has been particular criticism of the application of so-called mark-to-market rules, blamed for putting some firms in difficulty as markets have plunged.