The attorney general has agreed to allow an application for a fresh inquest into the death from asthma of a nine-year old girl.

He acted after hearing new evidence linking Ella Kissi-Debrah's death to illegal levels of air pollution near her home in south London.

Lawyers acting for the family said it was a "hugely important" step.

No individual death has previously been officially linked to illegal levels of air pollution.

In August, Ella's mother, Rosamund Adoo-Kissi-Debrah, delivered a 100,000-signature petition to Attorney General Geoffrey Cox calling for a new inquest into her daughter's death.

He said: "I have concluded that there is new evidence which may alter the substantial truth of Ella's death.

"I am therefore able to give my permission for an application to the High Court to request a new inquest, based on the evidential test being met."

'The right decision'

Ella lived in Lewisham, south London, 25m (80ft) from the South Circular road - a notorious pollution "hotspot".

She died in February 2013 after experiencing three years of seizures.

During that time, local air pollution levels regularly breached EU legal limits. Her last fatal seizure happened during a spike in air pollution levels.

An inquest in 2014 found she had died of acute respiratory failure and severe asthma.

However, the attorney general's decision has now paved the way for a new inquest to determine whether "unlawfully high levels of air pollution" were partially the cause of her death.

Mrs Adoo-Kissi-Debrah said: "It's great, it's the right decision and now we can get to the bottom, really, of the health impact of air pollution on young people.

"Hopefully if we are successful, national government, local government and individuals have to do something about cleaning up the air. It is unacceptable that children in Britain today die from asthma."

Human rights lawyer Jocelyn Cockburn, from the firm Hodge Jones and Allen, is acting on behalf of the family.

She described the decision as "hugely strong" and said the implications went far beyond Ella's case.

"A wider inquest would look not just at what happened to Ella and the circumstances into her death, but what steps were taken and what lessons can be learned. To look at the wider implications for children's health in that area," Mrs Cockburn said.

"For me, this case gives an opportunity for those people in public office for protecting our health, to be asked questions and to be held to account and to come up with solutions so we can move towards cleaning up the air as quickly as possible."

'Striking association'

One of the grounds for calling a fresh inquest was that permitting illegal levels of air pollution was a potential breach of human rights under Article 2 of the European Convention on Human Rights - which protects the right to life.

Mrs Cockburn said: "A new inquest could mean that a wide range of "interested parties" could be called to give evidence. This could include the local authority, the Mayor of London along with the local NHS Trust and Defra."

The attorney general's decision followed a report by Prof Stephen Holgate, a leading expert on asthma and air pollution, which found there was a "striking association" between Ella's emergency hospital admissions and recorded spikes in nitrogen dioxide (NO2) and PM10s, the most noxious pollutants.

His report said there was a "real prospect that without unlawful levels of air pollution, Ella would not have died".

Ella often walked to school along the South Circular Road and Lewisham High Street, a journey that would take 30 to 40 minutes. Or she would be driven and have to sit for lengthy periods in traffic jams.

She was first taken to hospital in 2010 after a coughing fit that followed a spike in air pollution levels.

No link explained

She was subsequently admitted to hospital 27 times over three years. Many of these coincided with recorded peaks in air pollution.

Her mother said she had resuscitated Ella between 20 and 30 times while waiting for an ambulance.

She said that Ella had been treated in five separate hospitals but no medical professional had ever explained that air pollution could be making her asthma worse.

The next legal step is for the application to be taken to the High Court, which will decide whether it is "desirable or necessary" to have a fresh inquest.

While the High Court has the final say, it is highly unusual for the court to disagree with the attorney general. According to Mrs Cockburn, decisions made by the attorney general are "arguably unchallengeable".