Brian Reilly, 47, took money from unsuccessful deposits by people attempting to open accounts.
The customer services manager stole from prospective account holders who had not reclaimed their money. When questioned by bosses he admitted taking the cash and blamed stress and debts.
Reilly, from Johnstone, pled guilty at Glasgow Sheriff Court to embezzling £128,538 from the National Savings Bank on Boydstone Road in Glasgow's Pollok area between February 2007 and July 2010.
The court heard the bank carries out identification checks for new customers who want to open accounts and deposit money.
If they fail the checks they are informed and given documents to recover the cash they attempted to deposit.
However, if after three months the money is not claimed it is moved into a holding account. It was from this account Reilly moved the money into his own.
Harry Findlay, prosecuting, told the court that an audit in July 2011 showed that transactions relating to two different customers had been transferred in to the same bank account.
Further investigation showed two more transactions for two other customers had also been transferred into the same account.
Mr Findlay said the person processing these transactions was Reilly.
The court heard 38 transactions amounting to £107,018 were made to one of Reilly's accounts and another eight transactions totalling £21,520 were made to another.
Reilly was suspended and an internal investigation took place. At a meeting in August 2011, he admitted responsibility for the embezzlement and claimed to have suffered from stress and debt problems.
When later questioned and arrested by police, he told them: "I went through all this, I'm ashamed, I have ruined my life I know I have."
There was no recovery of any of the money.
Sheriff Norman Ritchie QC deferred sentence.