Parents taking children to sports clubs regularly are affected
The head of a government scheme to vet adults who work with children has hit out at criticism of the initiative.
Sir Roger Singleton, chairman of the Independent Safeguarding Authority (ISA), says people need to "calm down" and consider the issue "rationally".
The ISA came under fire after it emerged that parents who regularly give children lifts on behalf of sports or social clubs will have to face checks.
People who ignore the new regulations face fines of up to £5,000.
The Home Office's Vetting and Barring Scheme, which is designed to protect children from paedophiles, covers adults who are in regular contact with young people.
Anyone taking part in activities involving "frequent" or "intensive" contact with children or vulnerable adults three times in a month, every month, or once overnight, must register with the ISA.
All school governors, doctors, nurses, teachers, dentists and prison officers must also sign up.
People must go through a series of checks and have their names put on a list of approved individuals. Those seeking employment will have to pay £64 for the checks - but the charge will be waived for volunteers.
Informal arrangements between parents will not be covered.
Sir Roger, whose agency will run the vetting scheme, said: "We need to calm down and consider carefully and rationally what this scheme is and is not about.
"It is not about interfering with the sensible arrangements which parents make with each other to take their children to schools and clubs.
"It is not about subjecting a quarter of the population to intensive scrutiny of their personal lives and it is not about creating mistrust between adults and children or discouraging volunteering."
He added: "It is about ensuring that those people who have already been dismissed by their employers for inappropriate behaviour with children do not simply up sticks and move elsewhere in the country to continue their abuse.
"And it is about bringing an end to the need for repeated CRB checks which so many people have found irritating. ISA registration is a one-off process for a single fee."
The scheme, which covers England, Wales and Northern Ireland, will be phased in from next month, and registration and checking will be mandatory from November 2010. A separate but aligned scheme is being set up in Scotland, to be introduced next year.
But critics claim it is threatening civil liberties and may deter volunteers.
The NSPCC children's services director Wes Cuell told the Sunday Telegraph the move could stop people doing things that were "perfectly safe and normal".
"The warning signs are now out there that this scheme will stop people doing things that are perfectly safe and normal: things that they shouldn't be prevented from doing.
"When you get this degree of public outcry, there is generally a good reason for it.
"I think we are getting a bit too close to crossing the line about what is acceptable in the court of public opinion.
"We don't want to throw the baby out with the bathwater."
Mr Cuell stressed that while it was important to strengthen rules to protect children from potential sex offenders, overzealous interpretation of the regulations could threaten civil liberties.
Children's authors, including Philip Pullman and Michael Morpurgo, have complained the requirement is "insulting" and say they will stop visiting schools.
Earlier this week, children's minister Delyth Morgan said safeguarding children was the government's priority and it was about ensuring people in a position of trust who worked with children were safe to do so.
The scheme was recommended by the Bichard report into the Soham murders of Holly Wells and Jessica Chapman by college caretaker Ian Huntley.