Barclays gave a Leeds firm and its owner overdrafts totalling £30,000.
But the company claims the bank's own credit rating service then gave it low scores, losing the business two long-standing suppliers.
When firms trading with Allied Machinery Ltd, of Junction Mills, Tong Road, Leeds, saw its Barclays "CreditFocus" score fall they refused to supply goods without cash up front – despite doing so for 20 years.
Managing director Mike Strother said previously the company had received scores of more than 50.
The first he knew of a reduction was when two suppliers refused to continue to provide goods on credit.
They said this was due to Allied Machinery Ltd's reduced CreditFocus rating – which at one point fell to 20.
He said his company was facing the difficulties of the recession like others. It had experienced difficult trading periods, but had recovered to make a profit.
Mr Strother said: "On the one hand Barclays lend you money – on the other they indicate you are a bad risk."
Allied Machinery had a 25,000 business overdraft facility with Barclays it occasionally used and he had a personal 5,000 overdraft facility.
Mr Strother said: "Barclays are more than happy to extend substantial credit to us, themselves – but this fact alone has no bearing on information Credit Focus provides by way of its score. I have complained only to be told that although Barclays provide the service, they are not responsible for the information or score they provide.
"I am expected to blame information providers such as Companies House and Experian who will only give limited information about how they score their subjects."
Mr Strother said the suppliers who declined credit did not quote Companies House or Experian – they quoted a low score on Barclays Credit Focus. He had asked Barclays to stop giving out negative information or a reduced credit score about Allied Machinery Ltd, but Barclays had simply said they were not responsible, as they do not provide the information and would not stop.
"My contention is that Barclays' name is on it – so they have control," he added.
A spokeswoman for Barclays said: "All credit information presented within Credit Focus is a market level opinion provided by Experian, who operate one of the most advanced databases of business information in the UK utilising a large number of measures to score the
creditworthiness of businesses. Business credit scores can fluctuate according to a business' recent or trending payment and business performance, and where a Credit Focus customer wishes to query their score, they can work with Experian to help take measures to improve their score."