Veteran children’s TV presenter Johnny Ball has claimed his outspoken views on climate change have sparked a malicious campaign which threatens to wreck his career speaking about science in schools.

The long-term science educationalist, who rose to fame in the 1970s and 1980s presenting science and technology programmes for youngsters, has built up a prolific public speaking career over the past decade, visiting up to 100 schools, science festivals and teacher training events each year to talk about the environment, maths and science.

But his bookings have dropped by 90 per cent over the past year and the 72-year-old has blamed this on harassment by extreme environmentalists who object to his dismissal of climate change as “alarmist nonsense”.

Mr Ball, father of TV and radio presenter Zoe, told The TES a website featuring pornographic images was posted online bearing his name, while another blogger stated he “should not be allowed near children”.

Since the former presenter of Think of a Number, Johnny Ball Reveals All and Think Again contacted police last week, both items have been taken offline.

An imposter also attempted to cancel Mr Ball’s booking at a training day for maths teachers in Northampton next month.

“This was clearly a criminal act aimed directly to damage me and my career business,” he said. “Since notifying the police of these acts aimed at damaging my name and reputation, the offensive web links have quite amazingly disappeared.

“People have every right to make up their own minds on my stance on many issues regarding children.

“But to deliberately smear my name in ways that are clearly criminal is so very disappointing. I would hope it is not the way fair and sensible debate is going in this far more open, modern society.”

Mr Ball, who has also written books on maths and produced five educational stage musicals, hit the headlines in 2009 when he was reportedly booed off stage after hitting out at the “bad science” of man-made global warming at an event at London’s Bloomsbury Theatre organised by comedian Robin Ince.

He previously spoke on the issue at the Royal Society of Edinburgh Christmas lecture and at the Manchester Science Festival in 2007.

He said: “The reason I take this stance is because several films have been introduced into schools which imply that the earth may not be able to sustain human life as we know it, in around 39 years’ time, which is unscientific, alarmist nonsense.

“Of course mankind is a great burden on the earth, but at every turn we are learning to manage and better control our impact and the damage we do . However, my main concern is that the alarmism is actually frightening schoolchildren to an alarming degree.

“It is suggesting to them that the previous generation have all but ruined the planet, and unless they switch standby lights off, for instance, we could all be going to hell in a handcart.

“This does nothing to promote confidence in our young. It sends the message that all technology is harmful and that we should reject much of it and return to a more frugal existence.

“Yet, in truth, great strides are being made. Gas-fired power stations now produce twice as much power for the same fossil fuel as they did 15 years ago. Cars have far cleaner exhausts and have doubled their mileage and tyre wear, and they are all recyclable or reclaimable. These are success stories.”

A spokesman for South Thames Police said the force was investigating Mr Ball’s complaints.

• Original headline: Johnny Ball: climate change zealots are out to ruin me