The Health and Safety Executive is to look into installers' criticisms of 'uninspectable' twin-pipe flue boiler systems after the tragic death of Elouise Littlewood.

The 26-year-old childcare assessor is believed to have suffered carbon monoxide poisoning after being found dead in her Barratt Homes-built flat on February 27, while her flatmate Simon Kilby, 31, remains in a serious condition in West Middlesex Hospital.

And now the Association of Registered Gas Installers (ARGI) has raised concerns about the system in the block of flats which it says is almost impossible to inspect because the pipes - which can be up to 60 feet long - are often concealed in ceiling voids or pass through neighbouring properties.

As many as 60 flats may have had faulty boilers in the months leading up to the tragedy with some tenants still without gas.

An HSE spokesman said the investigation continues and added: "If ARGI has these concerns and come to us with evidence we will look into it."