A "gentleman's agreement" that allowed vulnerable children, including some who may have been trafficking victims, who entered the UK alone to be sent back to France has been ended after an investigation.

The Landing in Dover report, by the Office of the Children's Commissioner (OCC), found the agreement allowed unaccompanied children to be sent back to France within 24 hours if they did not immediately ask for asylum.

The agreement was at odds with the UK Border Agency's (UKBA) duty to safeguard children and promote their welfare and has been ended after it was brought to the attention of UK Border Agency chief executive Rob Whiteman, Children's Commissioner Maggie Atkinson said.

Just over 1,700 unaccompanied children who entered the country in 2010 sought asylum, whilst a number of those returned to France under the UK/France deal may have been trafficked for exploitation, the OCC found.

It found children seeking asylum include those escaping war zones and persecution, and they are often hungry, ill, exhausted and distressed when they arrive, so much so that they are unfit to be interviewed by officials.

The report also uncovered excessive periods of detention before release into local authority care, due to the number and length of immigration interviews at the point of arrival.

Dr Atkinson said: "Children arriving unaccompanied in the UK are some of the most vulnerable that my office and society encounters.

"That is why we have continued to investigate how they are dealt with, working constructively with UKBA, to improve their treatment.

"This has been advanced through the end of the 'gentleman's agreement'. I commend Rob Whiteman for acting decisively."

The Refugee Council described the report's findings as "shocking" and urged the government to heed the recommendations to improve the screening system for children when they arrive, not just in Dover but in ports across the UK.

Donna Covey, chief executive of the Refugee Council, said: "We are very relieved that as a result of this welcome report, the disgraceful 'gentlemen's agreement' that has long put the wellbeing and safety of children at risk of harm and exploitation has now been put to an end.

"The report has shone a light on the lengths our government is prepared to take in order to pass the responsibility for children arriving here back to other countries."

The report resulted from an investigation by the OCC into the treatment of unaccompanied children asylum seekers when they first arrive in the UK.

Children's Minister Tim Loughton said: "This paints a historic picture.

"We published the first ever national action plan only two months ago to get a grip on these appalling crimes.

"It sets out a clear strategy for local areas to understand the severity of the problem in their areas; tackle it effectively; and put proper support in place for victims and their families."

He went on: "Sexual exploitation is child abuse pure and simple.

"We've given local authorities total freedom for the £2 billion annual early intervention grant to target the most vulnerable children and families.

"It's a false economy not to step in early to prevent problems escalating and leaving children open to abuse."