The leader of the nationalist Social Democratic and Labour party has been reported to Northern Ireland’s attorney general over claims he prejudiced the upcoming trial of a former soldier charged with killing civilians on Bloody Sunday.

Jamie Bryson, a loyalist blogger-activist, has complained to the region’s chief law officer about Colum Eastwood and remarks he made on Twitter and in a press statement about ‘Soldier F’.

On Thursday night Eastwood denied he was guilty of contempt of court and stood by his comments.

Soldier F faces prosecution for the murder of two men in Derry during the atrocity in 1972.

Eastwood made the comments both on Twitter and later in the Belfast Telegraph in response to revelations that T-shirts expressing solidarity with the former paratrooper were being sold on Amazon over the past few months.

In his letter to the attorney general, John Larkin QC, Bryson said: “Soldier F has not been tried before the courts and no determination has been made as to whether this individual killed anyone.

“This tweet by a senior politician, with a large social media following, is in my view clearly prejudicing the upcoming trial of Soldier F and infringing his article 6 rights to a fair trial and indeed running roughshod over the presumption of innocence which should be afforded to all suspects in any criminal proceedings.

“I believe that this is a matter of some gravity and is clearly a deliberate attempt to influence the outcome of the proceedings.

“As such I would request that the matter is reviewed and if Mr Eastwood is found to be in contempt of court then consideration should clearly be given to issuing proceedings against him in order to deter other nationalist politicians from trying to use their public platforms to infringe upon the rights of defendants in criminal proceedings.”

Eastwood said he “totally stood by” the remarks he made about the former paratrooper.

Soldier F denies murdering James Wray and William McKinney when the Parachute Regiment opened fire on civil rights demonstrators in Derry in 1972. Thirteen people died.

It has still not been established if Soldier F will be tried solely by a judge or in front of a jury during his trial. He will appear at Derry’s magistrates court in August.