Conservative leader David Cameron was tackled on the election trail over the alleged segregation of disabled children in the education system.
Accompanied by his wheel-chair using son, Samuel, Jonathan Bartley told Mr Cameron of the two-year struggle he had faced to get the seven-year-old into his local school.
He voiced concerns about Tory plans to end the bias towards inclusion of children with special needs in mainstream schools.
But Mr Cameron insisted he was trying to make it easier for families to get what they wanted for their children.
Mr Bartley said a bias against inclusion was "the wrong way to go".
"You are not representing the needs of children in mainstream education. You want to segregate disabled children."
But Mr Cameron, whose disabled son Ivan died last year, said that as the parent of a disabled child himself, he was "passionate" about helping parents get the education that was right for them.
He said he would make it easier for parents to get what was right for their child, be it inclusion in mainstream schools or a special school education.
The Conservative manifesto states: "The most vulnerable children deserve the very highest quality of care, so we will call a moratorium on the ideologically-driven closure of special schools.
"We will end the bias towards the inclusion of children with special needs in mainstream schools."
Mr Bartley tackled the Tory leader after he had delivered a speech on what he called the "broken society"
He said: "You are saying you want to reverse the bias towards the inclusion of children in mainstream schools. At the moment there is a bias against inclusion, not a bias for it, as your manifesto says."
"You talk about a broken society, it nearly broke up our family getting our son into school."
Mr Bartley had battled to get his son into St Leonard's Church of England School in Streatham. He added: "His two sisters go there, it's our local school, we have had to struggle for two years and in the end the secretary of state had to intervene. There is a bias against inclusion and you are saying there's a bias for it."
Mr Bartley, who runs the Liberal Christian think-tank Ekklesia, said he had decided to confront Mr Cameron as he took his son to a hospital appointment.
He said had been asked by a Conservative Party worker if he wanted to meet Mr Cameron, and had said yes.
He later said he thought they had been wanting a good photo opportunity.
Under the Labour, huge numbers of special schools have closed as the government pursued a policy of greater inclusion of children with disabilities.
The party has made recent attempts to make the special needs system easier and simpler for parents to negotiate.
But Mr Bartley said many parents were facing a "huge battle" to get their children into mainstream schools, he said.
"Labour haven't done well on this - this is not a party political issue - but for the Tories to come along and say 'We are going to actually reverse what we perceive as a bias' should be very, very worrying indeed.
He added: "What parent would not want their child to be educated in the local community with friends, with family, with brothers and sisters?"
He later told BBC News that there had been a move towards greater inclusion but that it had not been properly resourced.
"I hope this has put special educational needs on the agenda because it hasn't been so far."
The Liberal Democrats would end the presumption that the numbers of children in special needs schools would fall over time.
They also plan to encourage the co-location of special schools alongside mainstream schools with a similar age cohort.