Thousands of lone migrant children are living in squalid conditions or are vulnerable to smuggling gangs after being let down by European countries including the UK, a report has warned.
Youngsters face a culture of disbelief and suspicion, while authorities try to avoid taking responsibility for their care and protection, according to the Lords EU committee.
Peers said witnesses painted a "harrowing" picture of squalor, destitution and desperation that unaccompanied minors face across the EU.
The treatment of the young people has led them to lose faith in national authorities, the committee said, adding that vulnerable children have been exposed to smugglers and human traffickers. At least 10,000 unaccompanied under-18s are currently missing.
The committee also attacked the UK government for a "continuing reluctance... to show solidarity with its European partners in helping to relocate such children".
Sharp rises in the number of asylum-seeking children without parents or guardians have been reported around Europe amid the international migration crisis.
Nearly 90,000 lone minors sought refuge in the bloc in 2015 - a huge increase compared to just over 23,000 in the previous year. In the UK last year there were 3,043 applications from unaccompanied asylum-seeking children - a jump of 56% on the tally in 2014.
The committee said:
::EU member states are "fundamentally" failing to comply with their obligations under EU and international law to receive and protect children "in a manner that recognises their specific vulnerability".
::Conditions in camps in the French Channel ports are "wholly unsuitable" for children.
::The frequency of "non-medical age assessments", particularly in the UK, indicates a "widespread reluctance to believe unaccompanied migrant children's narratives".
::Evidence suggests a lack of "burden-sharing" between UK local authorities, with one council caring for 412 unaccompanied children, while many others had none.
Chairwoman of the committee Baroness Prashar said: "The current refugee crisis is the greatest humanitarian challenge the EU has faced in its lifetime.
"At the sharp end of this crisis are unaccompanied migrant children, who are being failed across the board.
"We found that these children face suspicion on arrival. They are seen as 'somebody else's problem', and the conditions they live in were described to us as deplorable and squalid.
"We found a clear failure among EU countries, including the UK, to shoulder their fair share of the burden.
"We deeply regret the UK Government's reluctance to relocate migrant children to the UK, in particular those living in terrible conditions in the camps near the Channel ports."
She added: "How can member states, including the UK, tolerate a situation where there are more than 10,000 missing migrant children in the EU?"
Ministers came under pressure earlier this year to do more to help child refugees in Europe. In May it was announced that Britain would take in unaccompanied children registered in France, Italy and Greece.
A Home Office spokeswoman said: "By legislating through the Immigration Act 2016 we have made crystal clear our commitment to bringing vulnerable children from Europe to the UK.
"More than 20 children have been accepted for transfer to the UK since the Act was given royal assent and the majority of these have already arrived.
"We are consulting with local authorities across the country to confirm available capacity and ensure appropriate support systems are in place.
"We are also in active discussions with the UNHCR and the Italian, Greek and French governments to strengthen and speed up mechanisms to identify, assess and transfer children to the UK and ensure this in their best interests."