Ian Paisley junior holds his High Court summons: his case will be heard tomorrow

Belfast High Court will to­morrow dec­ide if I'm in contempt of an order to reveal the name of a constituent who gave me information relating to the Billy Wright murder inquiry.

My father will be by my side in court. I could go to jail but jail is nothing new for a Paisley, nor is it something that frightens us. Dad served two six-month terms in Crumlin Road prison in 1966 and 1969. He did his time without complaint and, if it comes to that, I'll do mine in the same manner.

A contempt order isn't something I wear as a badge of pride. As someone who fully supports the courts and the forces of law and order, I've been placed in a dilemma. But public representatives have a duty, first and foremost, to those they represent. Billy Wright, the Loyalist Volunteer Force leader, was shot dead in 1997 by the INLA in the Maze prison. An inquiry was established into his murder.

Two years ago, whilst serving as a government minister in the Office of First Minister, I met a prison officer. He gave me details of a file-destruction policy on documents relating to Wright by the prison authorities. This prison officer, with over 20 years' experience in the service, was so perplexed by what he'd seen that he brought it to my attention.

I could have used that information in numerous ways. I could have called a press conference and highlighted what appeared to be evidence supporting the view that there had been a cover-up of the Wright murder. Such a move would have been self-serving.

I could have just buried the information and lived with the assumption that what the tribunal didn't know wouldn't hurt it, or taken the view that it would discover this information during its inquiry anyway.

Instead, I made a decision to assist the inquiry by forwarding the information to Billy Wright's father David, telling him how I came across it, and encouraging him to use it to get to the bottom of his son's murder.

I know this information assisted the inquiry. It helped open up several lines of investigation. The public interest was served well by my intervention. The only piece of information I retained was the name of my source. I had given that person an undertaking that he could meet and talk to me in confidence.

Maybe I suffer from having an old-fashioned notion of public service, that as a public representative I am the people's voice and I make a judgment call about how I use information that comes my way. My constituents are free to pass judgment on my actions at election time.

Since taking this action, all hell has broken loose. My letter to David Wright fell into the hands of the inquiry's legal team. It has pursued me with one agenda only – to force me to name my source.

I cannot do that. I've given my word, and as a public representative that's all I have. If I betray a constituent's trust, I will jeopardise forever the reputation of all elected representatives. If we can't protect our constituents, we will no longer be able to fight for the public good. We will be emasculated of the power to change society for the better.

I accept there's a fine line to walk. If I was covering up a crime, or a criminal, I would have no justification for silence. But my action protects a person who believes his position in the prison service would be over and who cannot be guaranteed any protection from the authorities for whistle-blowing.

My source has shed light into a dark and murky world of authority. I am prepared to face the consequences – even if that means imprisonment – for refusing to obey an order of a court I deeply respect. The name of my source goes with me to the grave.

All this has taken a huge personal toll on me. It's the first time a British elected representative has been pursued by the courts in this manner. The outcome will set a precedent for others in future. Sadly I detect that, in some quarters, this is not being treated as an important matter.

While I could be jailed tomorrow, it appears the Wright inquiry now recognises I have possibly more to gain from such a punishment than it does. I think that it's accepted that jail certainly didn't do my father's political career any harm, nor would it do my own.

So the inquiry is asking the court to take away part, or all, of my Assembly salary. It sees hitting my wallet as the best way of punishing me.

This case has already been expensive. I have to fund my own legal costs – they are not being met by the DUP or the Stormont Executive. I will be out tens of thousands of pounds. I am not getting legal aid. I would have liked to appeal the original court's decision and take this case all the way to the House of Lords, but I couldn't afford it.

Contrary to some public perceptions, I am not a millionaire son sitting on a family fortune. I have nothing more than my political salary. I have had to put my house on the Co Antrim coast up for sale. It's a lovely house, with fine views of Rathlin Island. After the hustle and bustle of political life at Stormont, it is my retreat.

If I am fined a huge amount, I face financial ruin. I have a young family – four children ranging from four to 14 years old. My family life has suffered enormously already. My eldest daughter told her mother that whilst she believes her dad is doing the right thing, it will be very embarrassing if he ends up in jail for doing his job.

My wife Fiona fully backs my actions. I couldn't have fought this battle without her rock-solid support. But this case has caused her extreme anxiety and many sleepless nights. She is particularly concerned about the effects the court's decision will have on our children who are all very close to their daddy.

The case has also meant that the lion's share of my time has been spent on preparing a defence and meeting with my lawyers, rather than on working for my constituents which should be, and until now always has been, my number one priority. I have to ask, what public interest has the Wright inquiry served by pursuing me? Some predict that the inquiry will fail to resolve the issues surrounding Billy Wright's murder. Is the pursuit of myself aimed at distracting from such a possible outcome?

My father is disgusted that I have been taken to court in the first place. He has offered unshakeable support. But if he is mad at what has happened, then my mother is absolutely furious. Like any mother, she is extremely protective of her youngest son.