Daniel Holmes, the Welshman jailed for 10-and-a-half years for cultivating cannabis, has filed a judicial protest claiming the harsh sentence was discriminatory and arguing that his case was null on procedural grounds.

Mr Holmes’s new lawyers, Franco Debono and Michela Spiteri, filed the protest against the Attorney General and the Police Commissioner, holding them responsible for any damages he incurred.

The protest is the latest twist in the legal case of 35-year-old Mr Holmes who was 28 when he was arrested in June 2006 at his €300-per-month Gozo flat. He was caught growing cannabis plants, which, he always maintained, were for his personal use.

The lawyers quoted case law where, they noted, other men in very similar circumstances were jailed for far less.

A judgment given in 2005 stated that “there is discrimination when similar cases or people in similar circumstances are treated differently and there is no objective and reasonable basis for that different treatment”.

They also referred to a long-standing issue on the discretionary powers of the Attorney General to decide whether an accused should be tried before a magistrate or a judge, which decision made a big difference in terms of the maximum sentence that could be handed down.

Last year, a Constitutional Court found that such discretionary powers had breached the human rights of a drug trafficker.

The lawyers also pointed out that there were procedural problems with the case that rendered it null.

The Attorney General had noted a procedural error after a police report was not exhibited and was not included in the case file, as required by law. He had asked for the proceedings to be heard again within five days but, this time, the charges were not incorporated in the case file and, although there was a note by the magistrate saying that the charges had been read, the actual documents were not there.

There is discrimination when similar cases or people in similar circumstances are treated differently

This shortcoming rendered the process null, the lawyers argued.

The jail term that Mr Holmes had been given in November 2011 was upheld by an appeals court last October. Another year in prison will be added if he does not pay the €23,000 fine that was also imposed on him.

Unwittingly, the sentence made him a cause célèbre for drug reform campaigners who felt his punishment exposed glaring problems with the law and justice system.

Mr Holmes readily admitted that he was a heavy cannabis smoker when he left Wales and had been for some time.