Large sums promised to developing countries to help them tackle climate change cannot be accounted for, a BBC investigation has found.
Rich countries pledged $410m (£247m) a year in a 2001 declaration – but it is now unclear whether the money was paid.
UN Secretary General Ban Ki-moon has accused industrialised countries of failing to keep their promise.
The EU says the money was paid out in bilateral deals, but admits it cannot provide data to prove it.
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The Bonn Declaration is surrounded by confusion and has led to mistrust between developed and developing countries.
UN Secretary General Ban Ki-moon says any new financing agreement signed at Copenhagen must be clear. 
(Read more from news.bbc.co.uk)