Last week, the bank was forced to write off pounds 240m of the loans, the largest such loss in its history. It blamed the move on the slump in property values.
But Humphrey Norrington, the Barclays vice-chairman in charge of risk management, said 'corporate misjudgement' was also to blame.
'We completely misjudged the property market,' he told the Independent on Sunday.
The bank, he said, had conducted an internal investigation into the debacle. It had found 'all kinds of things' that were wrong, which he would not specify.
'We didn't think the property market would fall as fast as it did. It was a major misjudgement.'
He said that Barclays should not have, in effect, made itself the sole lender to Imry. Barclays' total exposure to the privately owned group amounted to pounds 440m, making it the biggest-ever property loan by a single British bank.
'We should not have taken on to our books so large a proportion of the risk,' admitted Mr Norrington.
When asked whose responsibility that was, he said, pointedly: 'It was the general fault of many of us.'
According to Mr Norrington, Barclays first thought Imry might prove a problem at the end of 1989. He said that Andrew Buxton, the chief executive and chairman designate, had been 'appraised of the situation'. In July last year, despite the worries, Barclays doubled its exposure to the property company.
The problems came to a head in August this year when Castor Holdings, a Canadian finance company controlled by Wolfgang Stolzenberg, Imry's chairman, collapsed with debts of Cdollars 1.8bn ( pounds 800m).
Mr Norrington said the bank's due diligence on Mr Stolzenberg had been 'very little - although, I can assure you, we know a lot about him now'.
Mr Norrington's remarks are bound to increase the pressure on Mr Buxton, who faces mounting fury from shareholders over the bank's performance ahead of taking over the chairmanship on 1 January.
'My feeling is that Mr Buxton is too tainted to become chairman,' said one leading shareholder. 'He has lost too much credibility and has become a lame duck.'
Following earlier pressure from shareholders, Mr Buxton has already agreed not to combine the roles of chief executive and chairman, but to relinquish the former when he becomes chairman.
Shareholders are expected to press Barclays for an explanation of how the huge losses on Imry came about and, particularly, how the bank came to make a pounds 440m loan to one company.
Barclays has so far made little effort to explain itself to shareholders.
'We've had no explanation from Barclays so we will probably ask for some information next week,' a shareholder said on Friday. 'Who was responsible for what went on? It's very difficult to get to the bottom of it.'
Equally worrying for Barclays is the growing disquiet among branch and regional managers over the bank's problems and the new chairman. Many are angry at the controversy at the top of Barclays and are questioning whether Mr Buxton would have been appointed chairman if he had not been one of Barclays' 'ruling families'.
Mr Norrington admitted manager morale had been damaged by the Imry episode. One solution was to tighten lending procedures. 'We will be taking a more technical approach to judging winners and losers from now on. We want to give back to our managers, who are suffering from a lack of confidence, the mechanism to start lending again.'
An increasing number of institutional shareholders believe that Barclays is almost certain to cut its dividend at the end of the year, and they would support such a move.
'There is now a 75 per cent chance of a cut, but that's good,' said one. 'We like companies to reflect their prospects and Barclays' prospects are not good.'
Another said: 'The Imry announcement hastens the dividend cut. We're pretty certain they'll do it and it is right to do so.'