Council officers have come under fire after sending council tax bills with residents' personal and bank details to the wrong addresses.
The Oxford Mail was alerted to the mix-up by a resident of Boundary Brook Road, Oxford, who received his neighbour's bill last week.
Kevin Bourton, 48, said he was furious with Oxford City Council, which declined to say how many bills were sent to the wrong place.
He said: "I find it absolutely disgusting. I phoned the number on the back and said I wanted to speak to a supervisor immediately.
"I was told someone would get back to me and I am still waiting."
The neighbour's details included his full name and address, his bank details, including the sort code and account number, and the date when the money was due to come out of his account.
Mr Bourton, who maintains respiratory equipment on behalf on the NHS and knows the importance of patient confidentiality, handed the bill directly to his neighbour, who did not wish to be identified.
"He was just grateful I returned it to him safely and he is perfectly happy his details are secure," he said.
"If I was in his position I would be demanding an explanation.
"I really don't see any reason for the details to be on the statement.
"If his bill got mixed up with mine, how many other times has his happened? You are not going to persuade me this is the only mistake of this nature. There should be fail-safe checks.
"There have been enough stories of people's bank account details lost by different Government departments and I don't understand why someone from the council hasn't got back to me.
"They don't appear to see it as a problem."
Earlier this month, the Oxford Mail reported how documents containing 200 people's financial details were found strewn across a road in Wantage.
A spokesman for the Information Commissioner's Office, a Government agency responsible for protecting personal information, said: "It is essential organisations transferring personal information do so securely."
Paul Warters, head of customer services at the city council, said 57,000 council tax bills had been sent out this month and information to date suggested the mix-up had occurred in a "very small number of cases".
However, the council did not say exactly how many bills had ended up in the wrong hands.
Mr Warters said: "That two bills should end up in one envelope is simply unacceptable.
"We are taking this up as a matter of urgency with the mailing company to ensure this does not happen again.
"We take confidentiality very seriously, and we expect any private contractors to live up to our own standards."
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