While mobile banking services are still available, customers who use online and telephone services are facing outages.
The problem comes just months after a prolonged period of IT troubles left TSB customers locked out of their bank accounts.
A Barclays spokesperson said: “We’re currently experiencing some technical problems – customers are still able to use Barclays Mobile Banking app to check their balance, make and receive payments.
“We’re on it, and as soon as it’s fixed we’ll let you know.”
A number of business customers have complained that they are currently unable to organise tomorrow’s payments for staff.
Services in-branch are also currently intermittent, the bank has acknowledged, leaving many fearful ahead of the weekend.
Barclays did not respond to Sky’s enquiries about what was causing the outage, nor when they expected it would be resolved.