James Hipwell, a financial journalist who was jailed in 2006 for writing about firms whose shares he owned, told the Leveson inquiry into media ethics that he overheard showbiz journalists openly discussing the practice.

In a statement read to the inquiry, Hipwell said: “I witnessed journalists carrying out repeated privacy infringements using what has now become a well-known technique – to hack into the voicemail systems of celebrities, their friends, publicists and public relations executives.”

The statement added: “The openness and frequency of their hacking activities gave me the impression that hacking was considered a bog-standard journalistic tool for gathering information.”

The paper’s publisher Trinity Mirror has insisted that its journalists work both within the law and the Press Complaints Commission’s (PCC) code of conduct.

But Hipwell told the inquiry that he had never been given a copy of the PCC code during his employment at the paper, which was under the editorship of Piers Morgan at the time.

He added that he was seated next to the showbiz team when he worked at the tabloid, and revealed: “I would go as far as to say it [phone hacking] happened every day. It became apparent that a great number of stories… would come from that source.”

Hipwell even suggested that Morgan had been aware of the technique, stating: “Showbusiness is very close to his heart… and a lot of people who had worked on the showbusiness desk had come from the Sun and they were old friends. Nothing really happened on that desk without Piers knowing about it.”

Morgan previously told the Leveson inquiry that he had no reason to believe that phone hacking had gone on at the paper under his editorship.

Hipwell was jailed in 2006 for recommending stocks to readers that he had himself previously purchased at a low price. When the value of those stocks soared following his recommendations, Hipwell would sell them at a significant profit. He is reported to have pocketed almost £41,000 from the practice.

For the crime, Hipwell received a six-month prison sentence.