Liverpool FC's fan database has been hacked resulting in a serious data breach for around 150 supporters.
The club confirmed to the ECHO that season ticket holder information - including home addresses and bank details - were stolen from a club email account.
A staff email account is understood to have been hacked by a third party who the club believe is a malicious person or group.
A Main Stand season ticket holder who wishes to remain anonymous said they were told of the data breach by email.
The fan said they were told some of their personal data was contained in an attachment to an email in the compromised account.
The club also said there is no evidence to date of any fraudulent use of personal information and they have notified people are believed to have been affected.
The supporter said the club offered a free 12-month Experian credit check as a gesture of goodwill.
The fan told the ECHO: "I received a number of emails from the club and didn't realise the seriousness of the situation at first as we do get a lot of marketing ones from them.
"As soon as I did, I got in touch with the club straight away but they didn't seem to take the concerns I raised particularly seriously and I am still waiting for the call back I was promised.
"The initial emails I received said my personal data in the email attachment in question included my name, email address, date of birth, membership number and billing address, but not my bank details.
"However the person I spoke to over the phone told me all the details they had on record for me - including my bank account number and sort code - would have been included.
"This is a critical time for me in that I am in the process of applying for a new mortgage so I am very worried this data breach may result in problems presenting themselves during the next few months.
"The person I spoke to over the phone completely dismissed my concerns over potential problems with my mortgage if my information was compromised and said everything would be fine but I do not necessarily believe that will be the case.
"I'm really disappointed LFC have let themselves be been compromised in this manner and am surprised my information seems to have been so easily stolen, while the club seem so relaxed in their response to it.
"None of my friends with season tickets seem to have been affected but there are tens of thousands of season ticket holders - and hundreds of thousands of club members - who the club hold similar information for.
"I am wondering just how many more people have been potentially affected by this and what the club are going to do to stop it from happening again?".
A Liverpool FC spokesperson said: “We take privacy and the security of the personal information we hold extremely seriously. Unfortunately we have determined that recently there has been unauthorised access to certain data held by the Club.
"Upon discovering the incident, we immediately took steps to ensure that no further unauthorised access would be possible.
“We promptly launched an investigation and have informed the UK’s data protection authority and the police of the incident. We have no evidence to date of any fraudulent use of personal information and have notified people who at this stage we know have been affected.
"We have also set up a dedicated team to help with any questions or queries that they may have. We continue to monitor for suspicious activity and take steps to make enhancements to our systems to prevent a similar incident reoccurring.”
