The Metropolitan Police Service (MPS) has been ordered to pay £5,000 each to four women for failing to investigate allegations of slavery.
The women, who had arrived in London from Nigeria as children, said they were beaten and emotionally abused by families they were forced to work for.
The High Court said the force's "failure to investigate" breached the women's human rights.
The Met said it deeply regretted the women did not get the service expected.
The force had originally argued it could not carry out an investigation because the women would not co-operate.
But the court dismissed this claim as "untenable".
Mr Justice Wyn Williams said in his judgment the Met "did nothing to commence an effective investigation".
"Their names were known to the police, they wanted their complaints to be investigated.
"They were directly affected by the failure to carry out an effective investigation."
The court heard the women were brought to the UK when they were aged between 11 and 15.
The women, who cannot be identified for legal reasons, said they were made to work for no pay in households in and around London between 1997 and 2006.
They complained that the police had infringed their rights under the European Convention for the Protection of Human Rights and Fundamental Freedoms by failing to investigate over a "significant" period of time.
Phillippa Kaufmann QC said: "They want an acknowledgement of how all of them have been treated and they want just satisfaction in the form of compensation."
She said that above all they want lessons to be learned so that others in the same predicament can be rescued.
Ms Kaufmann told the court the women were at all times "willing and prepared to have their allegations of abuse investigated".
"The problem is that... officers on the ground were repeatedly and, in every imaginable context, reluctant to discharge that duty and, whenever it was triggered, they repeatedly failed to take any steps to investigate the serious offences which were staring them in the face."
Ms Kaufmann said officers did not understand the very serious nature of the crimes and that there was a "worrying lack of concern" for the victims.
A spokesman for the women's solicitors, Bhatt Murphy, said after the ruling: "The Metropolitan Police Service has not apologised to any of the victims for failing to investigate their abusers in 2007.
"Instead it argued unsuccessfully in court that it did not owe a legal duty to investigate credible allegations of servitude unless those allegations were reported whilst the servitude was ongoing."
Following Friday's ruling, Scotland Yard it would consider the judgement.
In a statement, the force said: "The MPS takes all allegations of this nature seriously and the original matters alleged are now subject to a full and ongoing investigation by detectives from the SCD9 Human Exploitation and Organised Crime Command, which has already seen one woman jailed for 11.5 years for trafficking offences."
It said the way in which the Met investigates such crimes had changed significantly since the introduction in April 2010 of the dedicated unit of 39 detectives responsible for handling all human trafficking and immigration offences.