Teenager Holly Herdman clearly hadn't heard that it's not a great idea to mention you're having a party on a social networking site.

And it is especially unwise if you have been left in charge of the house while your parents are away.

What she claimed was intended as a drink with a few friends ended with a mob of teenage youths running riot through a small market town.

Public apology: Rampaging teenagers caused havoc at Holly's party

Cars were scratched, windows broken and many elderly residents were left terrified in their homes as the youths screamed and shouted in the street.

The 30-strong group had turned up to gatecrash the party but begun their rampage when 16-year-old Holly apparently tried to stop them coming in.

Holly's parents, who had been on a fortnight's holiday in Spain, found out about the party when a friend rang them the next day to say it was the talk of the town.

They telephoned Holly, who had been left in the care of a family member, and the teenager visited each neighbour to apologise personally.

But on their return Mr and Mrs Herdman, who run an antiques dealership, also decided to contact their local newspaper to try to make amends.

In an article in the Cornish Guardian, Mrs Herdman said: 'I want to take this opportunity to apologise for any upset caused. We were really shocked to hear what happened and are so sorry to everyone on the street affected by this.

'Holly has been around to apologise and we promise this will never happen again. We left her under the understanding she was being supervised but that obviously did not happen.'

War zone: A store which had its window smashed on the night of Holly's party

Trouble flared on the evening of August 6 when Holly invited five friends around to her parents' £350,000 terraced home in the normally sedate town of Lostwithiel in Cornwall.

She announced news of the 'Street Partayyyyyy' on her Bebo social networking site, which also contains references to drinking, smoking cannabis and pictures of the GCSE student with hand-rolled cigarettes.

Despite being underage, the group started drinking and other teenagers began to arrive. At 11pm, 30 youths turned up at the four-bedroomed property and demanded to join in.

The teenager had invited a handful of friends round for drinks but was horrified when up to 30 gatecrashers turned up

When Holly refused, the drunken and abusive mob began vandalising property and screaming and shouting until 4am.

One elderly resident, who asked not to be named, said: 'It was awful. They appeared to be drunk and were screaming. One girl was running around wielding a large stick  -  it was utterly terrifying.

'People felt frightened in their own homes and one woman told me she was too scared to turn the light on to call the police. It is totally unacceptable.'

Another neighbour added: 'It was just horrendous. We didn't get much sleep that night. We don't expect that kind of behaviour round here.'

Looking like Beirut: Annette and Martin Herdman from Lostwithiel in Cornwall have apologise for a party held by their daughter while they were on holiday

Police were called to the property at 2.40am and told revellers to turn the music down. They returned at around 4.30am  -  by which time most of the gatecrashers had dispersed  -  and had 'strong words' with those teenagers left at the Herdman's home. No arrests were made.

Holly, who is due to get her GCSE results today and hopes to train to be a nurse, said: 'There were only six of us to begin with just having a drink and listening to music. Then a couple of other friends turned up I hadn't seen for ages.'

Embarrassed: Images from Annette Herdman's Bebo site

She claimed other youths let themselves in when she heard shouting outside and went out to see what was going on. 'There was flour all over the floor and blood everywhere,' she said. 'People were cutting their feet on broken glass. I was really upset.'

Yesterday Mrs Herdman said. 'We had a right go at Holly over the phone. I was heartbroken.'