More than 72,000 Oxfordshire families have been caught up in the child benefit security lapse.

Two compact discs containing the names, addresses, national insurance numbers, dates of birth and, in some cases, bank details of 72,120 families in the county have been misplaced.

Although there is no evidence the discs have fallen into criminal hands, last night families were warned to monitor their bank accounts.

The discs went missing more than a month ago after they were put into an internal post system by a junior employee of Her Majesty's Revenue and Customs (HMRC).

Sensitive details of every family receiving child benefit in Oxfordshire and the names of their 131,345 children are on the password-protected discs.

Security experts warned the Oxford Mail that the information could be used for identity theft rather than embezzling bank accounts if it fell into the wrong hands.

Fraudsters could buy goods over the Internet or apply for credit cards under the victims' names, they said.

HMRC figures revealed 13,230 families in Oxford, 17,060 in Cherwell, 15,835 in south Oxfordshire, 13,870 in the Vale of White Horse and 12,125 in west Oxfordshire are at risk.

Yesterday, parents said they were worried despite Government assurances.

Mother-of-two Valerie Dixon, 31, from Trefoil Place, Greater Leys, Oxford, said: "It is terrible. I am angry. How can they lose CDs with people's details on with all the fraud that is going on nowadays?"

The maternity care assistant added: "It is like me working on maternity and giving all the patients' details out."

Emma Scott, 23, a mother-of-three from Rede Close in Wood Farm, Oxford, said: "I am a bit worried, I want to go and change my bank details over now.

"I do not want people after my details and going through my personal stuff - it is wrong."

The row has already led to the resignation of Paul Gray, chairman of Her Majesty's Revenue and Customs.

Boris Johnson, Tory MP for Henley, said: "I have had several emails from constituents anxious about this. Everyone makes cock-ups and things go wrong, but this is just unbelievable."

Prime Minister Gordon Brown and Chancellor Alistair Darling yesterday apologised for the security lapse, which saw the details of 25 million people across the UK go missing.

Oxfordshire County Council's trading standards department has advised people to check their bank accounts and credit card statements very carefully for the next couple of months.

Graham Cluley, a senior technology consultant for Abingdon IT security firm Sophos, said: "It is a huge lapse in security.

"Data like that is worth more than £1m. You would not put £1m in cash in an envelope and put it into an internal mail system.

"It is horrendously embarrassing for the Government. For something this high-profile to happen is disastrous.

"It is obviously alarming for the people affected - there are plenty of criminals out there who are ready to steal identities."