More than 4,500 children as young as 10 have been strip searched by the Metropolitan police over the past five years, data released under the Freedom of Information Act shows.

The figures obtained by the Guardian show 4,638 children aged between 10 and 16 were asked to remove their clothes and then searched by police between April 2008 and the end of last year. Just over a third were released by police without charge.

During a strip search, suspects are required to remove some or all of their clothing and can be asked to bend over and spread their legs. The police are allowed to do this if the person is suspected of concealing evidence, for example class A drugs or an object that could cause harm. Under the law, strip searches are not restricted to those under arrest; they can also be used where a person is detained as part of a stop and search procedure.

Between 2009 and 2014, Met officers strip searched just over 134,000 people, according to the figures, of whom 3.5% were children and 10.5% were female. In 2013, 803 children were subjected to the procedure, compared with 683 in 2009. In 2010, the figure reached a peak of 990.

Julian Huppert, a Liberal Democrat MP for Cambridge who unsuccessfully campaigned for children to be strip searched only if an adult other than police officers was present, said the figures obtained by the Guardian were "extremely worrying" and that he had raised the issue with Damian Green, the police minister.

Sophie Khan, legal director of Police Action Centre, a charity that advises people on their rights if they wish to pursue an action against the police, questioned whether strip searches of children were necessary.

"It is disturbing that the Met strip search children as young as 10 years old on a routine basis. Strip searching is an inhuman and degrading experience and children should not be subjected to such treatment unless there is no other feasible method to detect crime available to the police," she said.

However, a spokeswoman from the Met said Her Majesty's Inspectorate of Constabularies and Prisons undertook regular joint inspections of the Met's custody suites and records, and had found the use of strip search to be "proportionate and appropriate".

"The justification for a strip search must be recorded on the custody record by the custody officer, the search must be conducted by at least two officers of the same gender as the detainee and the Met custody toolkit directs that the search must be supervised by the custody officer (gender permitting)," she said.

She added that under-18s, or those who are mentally vulnerable, must have an appropriate adult present during a strip search, unless an urgent search is conducted due to the risk of serious harm, or the detainee objects to the presence of the appropriate adult and the appropriate adult agrees.

"Strip searching is a vital power in police custody not only to identify and seize evidence but also to ensure the safety and security of all detainees and staff," she said. "Each search must be based on an objective assessment of the need and proportionality to search the person to that extent. Legal safeguards are applied to ensure the welfare needs of the detainee are considered and met."

• This article was amended on 12 May 2014 to make clear that strip searches can be used in circumstances other than an arrest and to make clear that they do not always mean that all clothing has to be removed.

