Children’s television presenter Johnny Ball is getting agitated, waving his hands excitedly and squirming in his chair. I’ve just asked him whether, if Woody, his daughter Zoe’s five-year-old son, fell over in the playground, his grandad would want a teacher to give him a cuddle.

“Yes, I would expect a teacher to look after Woody if he fell down. I would expect a teacher to feel — he or she, one of Woody’s teachers was male — they could. He has been to nursery school for years. I am sure they have had times they have had to console or cuddle him.” says Ball.

The veteran entertainer, who has two sons in addition to his celebrity daughter, usually shuns controversy. But now he has come out fighting against the government’s plans to force anyone who wants to work with children to undergo a criminal check.

He’s aghast, too, at the prevailing climate of opinion that touching children is something that should be avoided by those who work with them. “It is like George Orwell’s 1984,” says Ball. “A quarter of adults will have to be checked. We all brush up against children. The fear we are instilling in them is abhorrent. It really is,” he splutters.

It’s nearly 30 years since his children’s maths television programme Think of a Number. His career has been partly built on his gift for enthusing children about maths and science. Ball, a former Butlins redcoat, uses touchy-feely tricks such as getting them to try to pick him up with their fingers, or to push against him with rigid arms to demonstrate the stages of matter.

But now he believes the atmosphere around children is becoming toxic. If the Safguarding Vulnerable Groups Bill, currently going through parliament, is passed it will introduce a far more stringent vetting system for anyone wanting to work with children. All teachers and some others, such as hospital staff, who work with children already have to be vetted but the new proposal means thousands more people will need to be checked for criminal convictions, at a cost of £36 a time.

Their names will be placed on an online register and if they change jobs they will have to pay again to be vetted anew. Employers who let unvetted staff work with children will face a £5,000 fine.

The move follows the murders of the Soham schoolgirls Holly Wells and Jessica Chapman by caretaker Ian Huntley four years ago and is aimed at trying to stop paedophiles getting access to children. As Esther Rantzen pointed out last week in this newspaper, “unscrupulous and cunning” abusers have “taken jobs as school bus drivers, sports coaches and youth club leaders to gain access to children”. If just one murder is prevented by the bill — won’t it be worthwhile? Ball, like other critics of the proposal, believes it is taking a sledgehammer to crack a nut. He argues it will fail to stop child abuse and is full of stories about the many decent, loving parents and children who will be caught in its red tape.

“Some of the stories about checking are already quite ridiculous,” he says. “There was the deputy head who got a new headship. He arrived at his new school, and because he didn’t have his CRB (Criminal Records Bureau) clearance he couldn’t go in and have contact with the kids. He had to stay away from them for two weeks until the clearance came through.”

Then there’s the father who was stopped from leading the walking bus to his son’s primary school because he hadn’t been cleared. “He couldn’t walk with his own child and shepherd them to school,” says Ball.

Parents wanting to go on a school trip with their child’s class, teenagers volunteering to help youngsters with their reading, babysitters, fathers runing football teams — all will be subject to continuous criminal checking under the new law.

Ball himself adopts a commonsense approach. When a child cut herself at a science day he was taking part in at Imperial College London, he remembers “teachers were beside themselves with worry regarding the implications, with no thought to the child. I said, ‘I take full responsibility,’ which received cries of ‘Thank goodness, but are you sure we are in the clear?’ I took the girl, aged 13, into the ladies’ loo, having sent her friend ahead first to check it was empty. We washed the cut and stuck a plaster on.”

Would he do the same now? He smiles and says: “Kids revelled in these projects. I used to explain the laws of probability with two children’s cap guns. I no longer do that. You can no longer give a child a toy gun to explain the laws of probability.”

Ball says he has never been vetted and doesn’t intend to be. He still does dozens of workshops with children and says it would “break my heart if I couldn’t carry on”. “I am not vetted at the moment. Twice I have been asked and I say my reputation is there for all to see. When I come to a school I am just like any casual employee that must be beholden to the common law so why does anyone need anything else? Why would you need the surety of a third party? I will go ahead on that basis.”

The worst thing, he says, is that the bill won’t stop paedophiles. “Had these changes in the law been in place at the time they would not have stopped the Soham murders. Our existing laws were adequate to stop the Soham murders. Since Cain slew Abel, murder is in the human psyche. This is pointless and irrational.”