The Solicitor General will ask the Court of Appeal for the go-ahead to challenge a judge’s ruling stopping him from taking legal action against a protester who held up a sign outside a court.

Trudi Warner was arrested outside Inner London Crown Court in March last year for holding a sign outside an entrance used by jurors before a trial involving members of the climate group, Insulate Britain.

The sign read: “Jurors you have an absolute right to acquit a defendant according to your conscience.”

Last month, Mr Justice Saini dismissed a bid by Solicitor General Robert Coutts, a senior government legal officer, to proceed with High Court legal action against Ms Warner for contempt of court following her protest.

The Attorney General’s Office (AGO) confirmed on Wednesday that the Solicitor General applied to the Court of Appeal for the go-ahead to challenge the decision on Monday.

A spokesperson said: “The High Court’s judgment in this case has raised important questions about protecting jurors from interference which is why the Solicitor General is seeking permission to appeal.

“Contempt of court is a serious matter and the power to issue proceedings is used sparingly.”

Ms Warner was arrested after being seen on CCTV outside Inner London Crown Court for around 30 minutes with the sign on the morning of March 27 2022, the first day of the trial involving climate protesters, but she did not speak to any members of the public.

Later that day outside the same court, she joined a protest over how the judge in the trial, Judge Silas Reid, had overseen previous cases involving Insulate Britain members after he instructed jurors to set aside views they had on climate change when deciding cases.

After the AGO announced its decision to take legal action against Ms Warner last September, hundreds of people held similar signs outside courts across the country in solidarity.

Lawyers for the Solicitor General told a hearing last month that Ms Warner, a retired social worker from Walthamstow, east London, had committed contempt of court by “deliberately targeting” jurors outside the court.

But barristers for Ms Warner said she was acting as a “human billboard” to advertise a “vital constitutional, if occasionally used, safeguard against unjust prosecutions”.

In his ruling, Mr Justice Saini dismissed the Solicitor General’s claims, stating that Ms Warner’s conduct did not amount to an “actionable contempt”.

He said the placard “reflected in substance what is recognised as a principle of our constitution” and that a criminal prosecution “is a disproportionate approach to this situation in a democratic society”.

Responding to the Solicitor General’s decision, Jennine Walker, legal manager at the Good Law Project, said: “The High Court was quite clear that there was no basis to take action against Trudi when it threw the case out last month.

“The Solicitor General’s decision to appeal is chilling evidence of how far removed the government is from truth and justice and the lengths it will go to try and silence protest.

“The UK Government is not doing enough to prevent the damage caused by the climate crisis. Yet people like Trudi who call them out are threatened with jail.

“This case exposes the warped priorities of a government with no answers to the big problems.”