Parents who regularly ferry groups of children on behalf of sports or social clubs such as the Cub Scouts will have to undergo criminal record checks - or face fines of up to £5,000, it was disclosed today.
They will fall under the scope of the Government's new Vetting and Barring Scheme, which is aimed at stopping paedophiles getting access to children.
The Independent reports that the scheme could cost the British public at least £170m.
Failure to register with the Independent Safeguarding Authority, the Home Office agency which administers the scheme, could lead to criminal prosecution and a court fine.
The clubs themselves also face a £5,000 fine if they use volunteers who have not been cleared.
Parents who host foreign pupils as part of school exchange trips will also have to be vetted.
A total off 11.3 million people in England, Wales and Northern Ireland are expected to register with the ISA.
All 300,000 school governors, as well as every doctor, nurse, teacher, dentist and prison officer will also have to register because they come into contact with children or "vulnerable" adults at work.
The scheme was recommended by the Bichard report into the Soham murders of Holly Wells and Jessica Chapman by school caretaker Ian Huntley.
Huntley was given the job despite allegations of sex with underage girls in his past, which were not passed on.
It will be the biggest of its kind anywhere in the world and involve unprecedented delving into the subject's personal and employment history.
Two hundred case workers based at the ISA in Darlington will collect information passed to them by the police, professional bodies and employers and rule on who is barred.
Even those, like Huntley, without a criminal record, could be barred if officials are convinced by other "soft intelligence" against them.
It is estimated that the number of people facing a ban will double to 40,000 once the scheme is up and running.
Unlike previous lists of barred individuals, everyone registered with the agency will face continuing monitoring, with existing registrations reconsidered if new evidence is disclosed.
Its creators hope the scheme will reduce the risk of abusers being allowed to gain access to children and abuse their trust.
But critics, including children's authors, have criticised the scheme.
His Dark Materials writer Philip Pullman said the database was "corrosive to healthy social interaction" and has pledged to stop visiting schools to carry out readings in protest.
Criminal penalties, including jail terms, for employers giving sensitive jobs to those who are already barred, come into force next month.
From November next year workers taking new jobs which qualify for the scheme must be registered.
Any activity which involves contact with children or vulnerable adults three times in a one month period, every month, or once overnight, qualifies, as do jobs in specified places such as schools, prisons and children's homes.
Registration will cost £64 in England and Wales, but unpaid volunteers will be exempt from the charge.
Officials predict nine out of 10 people who apply to register will have no additional information held on them by the ISA and so will not require more detailed checks.
A Home Office spokesman said "informal" arrangements between parents to offer lifts would not be covered.
He said: "The Vetting and Barring Scheme does not cover personal or family relationships, so parents making informal arrangements to give lifts to children will not have to be vetted.
"However, anyone working or volunteering on behalf of a third party organisation - for example, a sports club or a charity - who has frequent or intensive access to children or vulnerable adults will have to be registered with the scheme. For volunteers, registration is free.
"We believe this is a commonsense approach, and what parents would rightly expect.
"The UK already has one of the most advanced systems in the world for carrying out checks on all those who work in positions of trust with children and vulnerable adults.
"Set up in the wake of the Soham murders, the new Vetting and Barring Scheme will, from October this year, ensure these regulations are even more rigorous."
Liberal Democrat home affairs spokesman Chris Huhne said the system was a "disproportionate response" that risked deterring volunteers from coming forward.
"The worst unintended consequence would be if it stopped people and charities from volunteering with children because of the fear of draconian fines," he said.
Shadow home secretary Chris Grayling said: "We are going to drive away volunteers, we'll see clubs and activities close down and we'll end up with more bored young people on our streets. The Government has really got to see sense."
The Office of the Information Commissioner said there were "inevitable" security risks of collecting large amounts of personal data.
But Assistant Commissioner Phil Jones said the ISA was "well aware" of its data protection responsibilities.
"Should individuals be barred from working with children, the ISA will inform them about the grounds for that decision.
"We will be maintaining close contact with the ISA to help ensure people's personal details are held in line with the principles of the Data Protection Act," he said.
Barnardo's chief executive Martin Narey, former director general of the Prison Service, said: "If the vetting and barring scheme stops just one child ending up a victim of a paedophile then it will be worth it."
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