The inquest into the Novichok poisonings in Wiltshire could become a public inquiry if issues of national security become relevant, a coroner has said.

Dawn Sturgess, 44, died and her partner, Charlie Rowley, fell ill months after former Russian spy Sergei Skripal and his daughter Yulia were exposed to the nerve agent in Salisbury.

They collapsed in June 2018 after encountering a perfume bottle believed to have been used in the poisoning of the Skripals and then discarded. Mr Rowley recovered but Ms Sturgess died on July 8.

Baroness Hallett, a retired Court of Appeal judge, was appointed to hear the inquest after High Court judges ordered the Wiltshire coroner to widen the scope of the inquiry.

In a written ruling following a pre-inquest review last month, Lady Hallett said some documents disclosed “in an exceptional case such as this will inevitably be of a highly sensitive nature”.

The Home Secretary is likely to claim public interest immunity so the documents would be excluded from the inquest, Lady Hallett said.

She previously said the hearing would examine whether Russia was responsible for the chemical attack, and where the substance used to poison Ms Sturgess came from.

Some evidence could be redacted and “material considered central to the investigation may have to be excluded from consideration”, Lady Hallett said.

“I think it is highly likely that I too will reach the stage when I must invite the establishment of a public inquiry but as yet I have a limited knowledge of the nature and extent of the material,” she said.

“I shall therefore reserve my decision until the inquest legal team and I have a better understanding of the material to be disclosed.

“But, as I made clear during the hearing, I am determined that this investigation should not be hampered by the kind of delay and unnecessary additional cost experienced by others.”

Lawyers representing Ms Sturgess’s family and Mr Rowley had wanted the inquest to be held under the terms of Article 2 of the European Convention on Human Rights.

This would mean the hearing was widened to consider “how and in what circumstances” Ms Sturgess died, but Lady Hallett said the inquest would focus on determining “who, when, where and how” her death occurred.

“Nonetheless it is well-established that as coroner I have a broad discretion in determining the scope of an inquest and that, even in a Jamieson inquest, scope can be broad,” she said.

“There is therefore the family’s interest, a public interest and the legitimate interest of a coroner inquiring into Ms Sturgess’s death in establishing if there is sufficient reliable evidence that a foreign state was involved in a lethal poisoning on British soil.

“My provisional view of scope, therefore, is that I should investigate all the issues set out by counsel to the inquest.

“Investigating them seems at present the only way to understand properly the ‘how’ of Ms Sturgess’s death. I cannot conduct a full, thorough and effective investigation into the death of Ms Sturgess and the acts and omissions that caused it without investigating the issue of possible Russian state responsibility.

“Furthermore, this is likely to be the only opportunity for such a thorough investigation in a legal forum.”

Two Russian nationals have been accused of travelling to the UK to try to murder Mr Skripal with Novichok, smearing the highly toxic substance on the door handle of his home in Salisbury.

Evidence gathered by intelligence agencies led the Government to conclude the men were officers from the Russian military intelligence service, the GRU.

The suspects – known by aliases Alexander Petrov and Ruslan Boshirov – were caught on CCTV in Salisbury the day before the attack.

Moscow has repeatedly denied any involvement, with President Vladimir Putin claiming the two suspects were civilians, and the pair stating in an interview that they were tourists visiting Salisbury Cathedral.