The Sun's head of news, Chris Pharo, will no longer stand trial for a charge of conspiring to commit misconduct in public office involving a prison officer, a jury was told today.

At The Sun corruption trial at Kingston Crown Court, Mr Justice Richard Marks QC told the jury that they would be asked not to return a verdict on Count 7 in the two-month case.

Count 7 alleged that Mr Pharo had conspired with a Sun journalist and a prison officer at HMP Swaleside to commit misconduct in public office between August 2007 and February 2009.

The judge's direction – following two days of legal argument at the trial – means that the total number of counts on which the jury will return a verdict has shrunk from nine when proceedings began in October to six now.

Mr Pharo, 45, faces three remaining counts of conspiracy to commit misconduct in a public office.

Alongside him in the glass-walled dock of Court 9 are five past and present Sun colleagues accused of various charges of conspiracy to commit misconduct in public office.

They are picture editor John Edwards, ex-managing editor Graham Dudman, former deputy news editor Ben O'Driscoll, Thames Valley reporter Jamie Pyatt and former East Anglia reporter John Troup.

All deny the charges.

The 12 jurors – wearing, with the judge's permission, brightly-patterned Christmas jumpers in aid of Save the Children – were informed of the change shortly before 1pm today.

Addressing them, Mr Justice Marks said: "For reasons that I need not go into at the present time my intention, having considered the matter with counsel, is to discharge you from giving a verdict on Count 7."

He added: "The evidence in the count however remains relevant," saying that that evidence – two Sun stories about the discovery of £30,000 heroin at HMP Swaleside and the throwing of a Freeview box over its walls – would remain in their files.

Mr Justice Marks is due to give his legal directions to the jury this afternoon, followed over the coming week by closing speeches from defence and prosecution counsel.