Children threatened with Tasers more than 500 times last year, charity reports
Police used Tasers when dealing with children at least 538 times last year and fired them on 43 of those occasions, according to a new report.
The total number includes occasions when officers drew their Taser, aimed it at a child, or fired it.
More than a quarter of the incidents (147) were against children aged 15 or younger and the youngest child fired on was 12, figures released to the Children's Rights Alliance for England (CRAE) by 44 English and Welsh police forces under freedom of information laws showed.
The charity defines children as under-18s - the measure used by the United Nations, which has called for the use of Tasers against children to be banned.
The campaigners warned that even if Tasers are not fired, brandishing them or using them as a threat can cause children "immense fear and distress".
Separate data also showed that so-called "spit hoods" were used on children, with the youngest 15 years-old, on at least 24 occasions by police in England in the first nine months of 2016, which can be "extremely distressing".
The charity also accused the Government of ignoring other recommendations from the UN Committee on the Rights of the Child, which in June urged Britain to follow its own law and stop children being placed in adult mental health wards.
Instead, 202 children experiencing a mental health crisis were admitted to adult mental health wards in 2015/16, a 43% increase on 2011/12, data released to the charity by by 33 English NHS Trusts or Foundations showed.
Of these, 10 of the children were under 15 years old - up from two in 2011/12 - and the figures prompted the campaign group to warn that being placed in adult wards can be "extremely frightening " for children with mental health problems.
The charity also highlighted already published figures showing more families with children are being illegally housed in bed and breakfasts (B&Bs) for longer than the six-week limit by local authorities.
Arguing that children are being "let down" by the Government, it also highlighted Department for Education statistics which showed that two boys a week aged five years and under were permanently excluded from school in 2014/15.
Louise King, director of CRAE said: "Our report reveals that Government has ignored the UN Committee's urgent calls to protect the basic needs and rights of some of our most vulnerable children including those suffering from poor mental health, living in B&Bs and treated badly by the police.
"The Government must take immediate steps to tackle the increasing failure to protect the human rights of children in England.
"CRAE is calling on the Government to introduce a child rights duty on public authorities so that when decisions are made which affect children, their rights are properly taken into consideration. This would ensure that the welfare of vulnerable children can no longer be ignored."
Barnado's chief executive Javed Khan said : "This new report makes alarming reading about the state of children's rights in England. It highlights how vulnerable children are not being kept safe from abuse while being denied basic things, like a permanent roof over their heads.
"The Government must keep its commitment to mental health, particularly for children and young people in care, a great many of whom don't have the support of a family to fall back on. It should use the Children and Social Work Bill to enshrine in law a child's entitlement to a proper mental health assessment when they enter and leave care.
"Sex education and healthy relationship lessons for all children should be made compulsory by Government as a matter of urgency. These lessons, which must be high quality and age appropriate, are key to equipping young people with the knowledge and skills to help them keep safe."
The Children's Rights Alliance is a coalition of 150 organisations and is supported by the Children's Society, NSPCC, Save the Children and Unicef.
Liberal Democrat health spokesman Norman Lamb said it was "appalling" that children with mental health problems are being "let down badly".
"Children and young people's mental health is still very much a Cinderella service in health and care and is terribly underfunded," he said.
"In Government I fought for an extra £250 million a year for children and young people's mental health, and yet frontline services report they actually get very little of that money because it is being used to plug gaps elsewhere.
"While the Government continue to bury their heads in the sand about the financial crisis facing health and care, young people who desperately need these services will continue being let down and that is simply not good enough."