Attempts by successive London mayors to clean up London's toxic air were "frustrated" by inaction by the Government, and inquest into the death of an asthmatic child has heard.

Nine-year-old Ella Kissi-Debrah died in Lewisham in February 2013 after suffering numerous seizures and making 27 visits to hospital with breathing problems over the previous three years.

An inquest ruling from 2014 that found she died of acute respiratory failure was quashed by the High Court following new evidence about the dangerous levels of air pollution close to her home.

Transport for London (TfL), three Government departments and the Mayor of London's office have been listed as interested parties in a fresh inquest into her death.

Also listed are her mother, Rosamund Kissi-Debrah, and Lewisham Council.

On Tuesday, Southwark Coroner's Court heard that as early as 2002 then-mayor Ken Livingstone was concerned about the lethal potential of nitrogen oxides (NOx).

In a strategy published at the time, he warned London would struggle to meet its air quality targets without "new effort" from the Government.

READ MORE: Ella Kissi-Debrah death: Lewisham Council moved at 'glacial pace' over illegal pollution

On Tuesday, Philip Graham, executive director of the Greater London Authority's (GLA) Good Growth fund, said the capital was not likely to meet legally binding limits on NOx emissions until at least 2025.

The targets, which were set by the EU, came into force in 2010.

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Despite the targets, NOx reductions were not a priority in the first phase of the Low Emission Zone, which came into force in 2008 and primarily sought to curb emissions of fine particulate matter.

Including NOx in the plans would have involved the regulation of private diesel cars, and not just commercial vehicles.

Mr Graham said Mr Livingstone would have been focusing on building consensus with his plans for cleaner air to avoid them becoming a "political football" that would be reversed by the next mayor.

The court also heard that although Boris Johnson made the decision not to extend the Congestion Charge Zone, studies indicated it would not have made much difference to emissions.

"I'm not trying to say he took the right decision or the wrong decision," Mr Graham said.

"I'm just noting that he wasn't flying in the face of advice that said this is going to lead to an (increase) in air quality and still took the decision."

He added: "The advice he was given was that the small drop in emissions had no discernible effect."

Mr Graham said that all three London mayors since the position was created in 2000 had found appealing to the Government for support "more of a source of frustration than an effective means" of change.

He said successive mayors have asked for more ambitious scrappage policies for the most polluting vehicles, changes to vehicle tax and clearer national frameworks around low emission zones.

They have also asked for a national alert service around pollution levels coupled with PR campaigns about the risks of air pollution similar to those around smoking and obesity.

Mr Graham said Sadiq Khan was appealing for funding to help with the cost of upgrading the bus fleet to electric, akin to the £5 million given to Boris Johnson for a previous round of upgrades.

"In few if any cases has the Government's response been a positive one," he said.

Ella's inquest has been listed under Article 2, the right to life, of the Human Rights Act, which scrutinises the role of public bodies in a person's death.

The inquest will consider whether air pollution caused or contributed to Ella's death and how levels were monitored at the time.

Other issues to be addressed at the inquest include the steps taken to reduce air pollution, and the information provided to the public about the levels, its dangers and ways to reduce exposure.

She may become the first person in the UK for whom air pollution is listed as the cause of death.