Nicholas Gaubert slipped into a diabetic coma on the top deck of a bus in Leeds and was shocked twice with the 50,000- volt weapon.

West Yorkshire Police claimed the Taser was used after an unconscious Mr Gaubert failed to respond to officers on July 13, 2005 – only a few days after the London terror attacks.

But the 34-year-old Headingley businessman said his experience was a frightening precursor to the shooting of Brazilian Jean Charles de Menezes by police in the capital a week later.

Now it has emerged that the constable who shot Mr Gaubert will not face any charge, and it is understood two senior officers facing action have been promoted, with one transferring to South Yorkshire Police.

Lawyers for Mr Gaubert have attacked the Independent Police Complaints Commission (IPCC).

Mr Gaubert said: "I feel disgusted at the way my complaint has been handled. It seems as though the IPCC are more concerned with protecting the police than dealing with the concerns of the public.

"It is now three years since I was Tasered and falsely arrested under the Terrorism Act. I was unconscious at the time of the attack with hypoglycaemia owing to my diabetes. I showed no aggression as I was unconscious and unable to respond to police demands. I have had no explanation or apology and it feels like the IPCC are denying me a full explanation."

Mr Gaubert's solicitor, Ifti Manzoor, of Sheffield-based Irwin Mitchell, said he and his client had been "kept in the dark" by the IPCC over an impending disciplinary hearing.

He added: "I find it astonishing that the IPCC are not prepared to divulge the nature of the misconduct charges that the two senior officers face or why the officer that fired the Taser is not to face charges.

"Instead, my client is expected to give evidence at a hearing where the officers themselves, the police force and the IPCC all know the exact nature of the charges and my client is not even given an outline. In circumstances where my client alleges appalling treatment by the police I would have expected the IPCC to make great efforts to ensure the matter was dealt with fairly and openly."

Mr Manzoor said the inquiry had taken longer than the probe into the de Menezes incident, which was completed late last year.

Nicholas Long, IPCC Commissioner for Yorkshire and Humber, said: "I have noted the comments of Mr Gaubert's solicitor with disappointment and frustration. I believe the comments are without foundation."

The IPCC's managed investigation concluded in November 2006 and a file was submitted to the Crown Prosecution Service, which decided last October not to press charges against the force or individual officers, he said.

"In December 2007 the IPCC directed that a disciplinary hearing should be held in relation to the conduct of two officers."

It was "unique for a joint disciplinary hearing to be held between two forces. It is hoped that the hearing can be held before the end of this year."

He said it had been explained to Mr Manzoor several times that it would be "wholly inappropriate and potentially prejudicial" for his client "to receive a full copy of the investigation report and certain other materials at this stage".

Last month the West Yorkshire force revealed that it was extending the use of the Taser with the weapon issued to officers in Wakefield and Halifax. Mr Gaubert said this was a mistake.

Both South and West Yorkshire Police have said they are working with the IPCC to bring the inquiry to a conclusion.