People visiting Salisbury in the immediate aftermath of the suspected spy attack have been asked to take action amid concerns over a substance used to poison Sergei Skripal and his daughter Yulia.

Public Health England (PHE) published the “precautionary advice” after the pair were found slumped on a bench in the Wiltshire city a week ago.

Tests subsequently suggested the pair were exposed to a nerve agent.

A third victim, Detective Sergeant Nick Bailey, was also admitted to hospital after falling seriously ill when he responded to the emergency, however his condition has since improved.

The PHE statement said those who visited areas where traces of the nerve agent were discovered – The Mill pub between 1.30pm last Sunday and closing time at 11.10pm on Monday, and the nearby Zizzi restaurant between 1.30pm Sunday and 9pm the next day – should take action.

This includes advice to:

– Machine wash clothing worn that day
– Double-bag clothing worn that day which would normally be dry cleaned and await further advice
– Wipe personal effects such as mobile phones, purses and wallets with baby wipes
– Hand wash jewellery

England’s chief medical officer Dame Sally Davies said she believed fewer than 500 people would have been in either venue at the times specified.

She said: “I want to reassure the general public that the risk to us all from this incident in Salisbury has not changed, and that the risk to us all remains low.

“Rigorous scientific analysis continues, but we have now learnt that there has been some trace contamination by the nerve agent in both The Mill pub and Zizzi’s restaurant in Salisbury.

“I am confident this has not harmed the health of anyone who was in The Mill pub or Zizzi’s restaurant.

“However, some people are concerned that prolonged long-term exposure to these substances may, over weeks and particularly months, give rise to health problems.

“I’m therefore advising – as a belt and braces approach – that people who were in [Zizzi’s or the Mill during the specified times]… should clean the clothes they wore and the possessions they handled while there.

“This is precautionary advice aimed at only those people who were at the venues at these times, which I believe to be below 500 people. I am confident none of these customers will have suffered harm.”

It comes as Armed Forces personnel continue to assist police.

Soldiers were seen at the South Western Ambulance Service station on Saturday as a vehicle was winched on to the back of an Army low-loader and taken away.

Police investigating the suspected attack have identified more than 240 witnesses and 200 pieces of evidence, Home Secretary Amber Rudd said.

Salisbury incidentA police officer stands guard at the Maltings in Salisbury (Andrew Matthews/PA)

The attack on Mr Skripal and his daughter was a “violation” of the city, the Bishop of Salisbury said.

The Rt Rev Nicholas Holtam told BBC Radio Solent: “There has been a violation of this place and this community and it is more than an attack on individuals.”

Cordons remain in place across the city as investigators in hazmat clothing continue to delicately scour for clues.

Wiltshire Police confirmed it has charged a man who breached one of the cordons on Friday evening.

Jamie Knight, 30, from Salisbury, is suspected of assaulting a police officer, common assault, criminal damage to a police vehicle and a racially aggravated public order offence.

He will appear before magistrates in Swindon on Monday.