Kaupthing, the Icelandic bank, is facing concerns over its balance sheet, the Observer reports.
According to the newspaper, the firm has risked over-extending itself through an aggressive expansion programme - and finds itself exposed in the harsher financial climate following the onset of the credit crunch.
Recent deals made by the bank include the part-acquisition of UK supermarket Somerfield and backing for the Shard of Glass, a proposed 300 metre tower in London.
Kaupthing also lends money to celebrity chef Gordon Ramsay's several restaurants, fashion chain Karen Millen, ultra-luxury property developers the Candy brothers and real estate powerbroker Robert Tchenguiz.
However, citing un-named "insiders", the report adds that the bank has "significantly eased back" on lending following its credit crunch worries.
Last quarter, Kaupthing declared a loss totalling just under $60 million - despite its having largely avoided dealing in the toxic sub-prime securities which have caused big write-downs at other banks.
Commenting, Alexandre Birry at credit ratings firm Fitch said: "Kaupthing has been subjected to negative marketing sentiment…our focus is on long-term trends.
"They have been growing [prior to the crunch] in capital markets and investment banking. Obviously the outlook [in these sectors] is weaker."
