Source | Video

In 2007, while investigating the Church of Scientology for Panorama, reporter John Sweeney had a dramatic on-camera confrontation with a church spokesman named Tommy Davis. The church was accusing the reporter of bias and it attempted to stop the documentary from being broadcast - a campaign backed by Scientology A-lister John Travolta. Sweeney has returned to investigate the church again.

I never meant to shout.

Strangers had been on my tail. Scientologist Tommy Davis and his colleague Mike Rinder - my handlers - had been on my case, day in and day out.

They had taken me to an exhibit called 'Psychiatry: Industry of Death' on Hollywood Boulevard, where a Scientologist told me psychiatrists set up the Holocaust. I feared I was being brain-washed.

And then I lost it - big time.

The Church of Scientology put out my impression of an exploding tomato onto the internet which millions had a laugh at courtesy of YouTube.

It was no way for me to behave. I apologised then and I apologise now.

Shortly after that programme, Scientology & Me, aired in 2007, I received a tip-off that Mike Rinder had left the church.

Three years on and my old adversary came to me to shed some light on what had been going on behind the scenes in the days leading up to my infamous meltdown and screaming session in Los Angeles.

Now an independent Scientologist, Mike is critical of the church and of its leader David Miscavige, who was actor Tom Cruise's best man at his wedding to Katie Holmes.

Mike, 55, wanted to meet and talk about his life in the church, which he was a part of from the age of six.

'Freed'

He began by telling me about the moment when he decided to get out: "I knew as I was walking out - that was the last time I would ever talk to my wife, my children, the rest of my family. I couldn't take it anymore. When I left I felt I had been freed."

Mike was subjected to what the church calls disconnection. His wife, daughter, son, brother and mother have cut him out of their lives.

Mike was one of a number of people we met who effectively grew up in the church and have since left.

Those who speak out say they can be deemed by the church to be enemies and subjected to disconnection - when all ties to family and friends are severed.

The church acknowledges some Scientologists choose to sever communications with family members who leave. The church says it is a fundamental human right to cease communication with someone. It adds disconnection is used against expelled members and those who attack the church.

During our investigation in 2007, black SUVs with tinted windows appeared to be following our team as we carried out interviews. A mystery man who we suspected was from the church also appeared to be keeping tabs on us at breakfast in our LA hotel each morning.

At the time, I put my suspicions of being under surveillance to Tommy Davis. He responded: "I don't know what you're talking about. It seems to me you're getting a bit paranoid."

Mike Rinder has since given me a different answer.

"Was I being paranoid?" I asked him when we met again.

"No, you were being followed. No doubt whatsoever," he told me.

Mike said he should know as it was he and Tommy Davis who were doing some of the covert surveillance.

Mike said he and Tommy were reporting back on our movements to David Miscavige's office every few minutes or so.

Through its UK lawyers, the firm Carter-Ruck, the church deny spying on us and reject Mike Rinder's version of events dating back to 2007.

Celebrity members

The public face of the church is as a force for good, perhaps most familiar to the public for their offers of free stress tests at their shopfront centres in major cities.

Its star members include Tom Cruise, John Travolta, Kirstie Alley and Juliette Lewis.

When I interviewed Alley in 2007 and put the question to her that many believe Scientology to be a sinister brain-washing cult, she replied: "Would you ever sit with a Jew and tell them that their religion is a cult?"

When I asked the same question of Juliette Lewis, star of the film Natural Born Killers, she replied: "Some people say women are really stupid and shouldn't have the vote."

The church said it is a religion and is recognised as such in America for tax purposes. It denies emphatically that it is a cult and has maintained that I am biased.

Many ex-Scientologists disagree with the celebrities who defend the church.

Amy Scobee, now in her mid-40s, is a former member who said she believes it is "a dangerous cult". She was a member from the age of 14, much of her time in the church was spent as part of what is known as the Sea Org - the highly-disciplined wing that effectively runs the church's day to day operations.

Private details

When Ms Scobee left and began to criticise David Miscavige and the church, intimate details of her sex life, before she was married, leaked to the St Petersburg Times in Florida newspaper.

The church admits sending the newspaper material about Ms Scobee's sex life, but said it was acceptable because the information was contained in an affidavit signed by her. They say it was not confidential.

Ms Scobee said she had disclosed those details but she believed they would remain confidential.

During our time in America for the latest Panorama, we were once again followed by people filming us, this time more openly than before. When we approached the people with cameras to ask them who they were with and what they were doing, they refused to answer our questions.

That is why I was somewhat grateful to Scientology's UK lawyers at Carter-Ruck when they sent the BBC photographs of me hugging Amy Scobee at the end of a long and at times harrowing series of interviews about her experiences.

The photographs were meant to demonstrate to my bosses at the BBC, once again, that I must be biased against the church as I was overly familiar with its critics.

This was, oddly enough, welcome proof that the people who had been following and filming us in the States were indeed working for the Church of Scientology. As Mike Rinder had said, I was not being paranoid - I was being followed.

The Secrets of Scientology:
A Panorama Special, BBC One, Tuesday, 28 September at 2100BST and then available in the UK on the BBC iPlayer. (UK)

or see Video link above.