It is believed a large rock was smashed into windows and the main door at the Blackpool Road premises of the national charity which helps vulnerable children.
It is the second attack on the shop and donation point near Ashton Park - not long ago a car was ram raided into the premises.
The latest damage was discovered by store assistant Jean Taylor who was shocked at what she saw when she went to open the store at 535, Blackpool Road on Sunday morning.
She said: " I came into work and there was a large stone about the size of a small sliced loaf and it had been repeatedly thrown at the windows. Three or four pieces of glass have all been shattered and the door is broken. I felt like crying."
Jean continued: "It wasn't so long ago that someone got a car and ram raided it into the shop and bust the doors. We had only just got everything back right and new doors etc. and now we're in the same position again. The worst thing about it is this is a children's charity. I can't understand why anyone would want to cause that sort of damage. It's mindless really."
She continued: "Staff and volunteers are genuinely upset about it .Our people care very much about what they do and where they work. It seems so senseless - it's upsetting. We got bollards and a new door and now this destruction ... not very nice at all. When I think of all the shops on Blackpool Road - why anywhere really, but why specifically us, a children's charity? I can't imagine."
After a clean-up yesterday the shop and centre opened for business this morning, pending the arrival of a team to secure the doors and windows this afternoon. But first there was more clearing up to do. Jean explained that while yesterday the door glass had multiple fractures it was still in place, but she believes high winds overnight dislodged the glass and buckled the door lock. Three or four tubs of clothes had to be dumped after they were shattered with shards of glass.
Julie Wilcock, Area Business Manager for Barnardo’s Retail, said: “This is such a sad affair for a charity store to be targeted in this way. The store has been open for some periods since the incident, but will need to be closed whilst the windows are replaced, impacting on sales and money that should be being raised for our cause of supporting vulnerable children. The matter has been reported to the police and we would ask anyone that has any information to pass this on to assist with police enquiries. We would like to thank the local community for their support.”
A police spokesman said the damage is being investigated and they had been advised the attack must have taken place between 5.30pm on Saturday and 9am on Sunday.