The huge investigation into the trafficking of children was started four years ago when a young girl came to the attention of police in London more than 500 times for a variety of offences, including pickpocketing.

Every time she was spoken to she claimed to be under 10, the legal age of responsibility, but officers discovered that she was a 14-year-old failed asylum-seeker from Bosnia.

The case threw up links to organised criminals smuggling children into Britain, and officers started the intelligence-based Operation Golf to ascertain the scale of the problem. Over the next two years 400 people were sent back to Romania, and crime in Oxford Street fell 28 per cent.

Since Romania joined the European Union, a new approach was needed and Operation Golf 2 began, not only to find the leaders of the gangs but also to cover the people coming to claim the children after their arrest.

The “parents” of these children, often armed with forged documents, would pick them up from the police station and have them back working on the streets the next day, with different names and alleged ages.

Several weeks ago officers patrolling the streets of London looking for young pickpockets and thieves arrested three young Romanians after spotting them attempting to shoplift. They were taken to a police station but they claimed not to speak English and to be under the age of 10.

An interpreter was called and their parents contacted. When the man claiming to be their father arrived to pick them up, officers checked and found that he was wanted for nonpayment of fines. He was arrested.

A short time later a woman arrived at the station claiming to be the mother of the children. When she was asked for identification, she produced a Romanian birth certificate for one of the children. An officer on secondment from Romania realised that it was a forgery and she was arrested in connection with producing a false document with intent to deceive. The children were also bailed to reappear while police make further inquiries.

This is the problem that officers have. Responsible adults coming to claim the children can often be the very people that put them out to work in the first place.

Earlier this month police conducted a series of raids on residences in East London looking for evidence of organised crime. At 7am officers burst into a small terraced house in Ilford and found 27 Romanian Gypsies, 16 of whom were children, some as young as 4 months, from several families, sleeping in the bedrooms, lounge and even the kitchen.

Superintendent Bernie Gravett, who heads Operation Golf 2, said: “The gangs operating in London are organised – what level that is something we need to look at. Certainly the crime types are different than we faced before.”

Sir Simon Milton, the leader of Westminster City Council, has called on the Government to get tough on foreign nationals committing crime in Britain. He said: “We know from intelligence that many of the individuals arrested by police today have been convicted previously, which is simply unacceptable and cannot be allowed to continue unchecked.

“I’m incredibly grateful to the Metropolitan Police and all agencies involved in today’s operation, which will no doubt make a substantial impact on crime in the capital, but without firm action by the Government, many of these criminals will be back on our streets in no time.”

Times Recommends

• What makes the perfect mum?
• To keep me stress-free, no more awareness days, please
• What do lottery winners buy?