Journalists at the Guardian News and Media (GNM) group are being asked to attend media law refresher courses, after one of their reporters was referred to the Attorney General.
The reporter had put the name of a juror in the Harry Redknapp trial on social networking site, Twitter.
Such an action could have placed the entire trial in jeopardy, at significant cost to the taxpayer.
In a separate incident, a GNM journalist later added further information about the trial to Twitter, at a time when the jury were not in court. The judge at this point ordered a ban on the use of Twitter in the court room.
The case occurs just six weeks after the Lord Chief Justice, Lord Judge, issued new guidelines stating that journalists and legal commentators would no longer have to apply for permission to use Twitter, write texts or use email during court sessions.
A spokesman for GNM said: "The Guardian provides ongoing legal refreshers for editorial staff, including sessions relevant to court reporting, and we want to ensure journalists, especially those who may be tweeting, are reminded of the law in this area."
It is understood that journalists from other newspaper groups also fell foul of the law during the Redknapp trial.
The Attorney General's Office has confirmed that it is also investigating an alleged breach of a court order made by a reporter for the radio station Talksport on 17 November 2011.
Other incidences of breaches involving reporters from the Daily Telegraph, the Sunday Express, the Evening Standard and the People newspapers between June and November 2011 have been recorded but are not being investigated by the Attorney General's Office.
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