A mother said her toddler could have died after discovering a gas leak that had been poisoning them for weeks.

Samantha Charnley did not realise she and 20-month-old Alyssa Charnley-Baxter were breathing in toxic carbon monoxide every time the hot water was turned on.

She said Alyssa started being sick on a regular basis from the end of August but doctors at her GP practice, Becontree Medical Centre, were unable to find a cause.

It was only when she switched the heating on in her council home on Tuesday of last week, and Alyssa began crying, that 24-year-old Samantha smelled gas.

National Grid visited and turned off the supply immediately, confirming the boiler had been leaking and needed a new valve.

The pair went to hospital and although carbon monoxide was found in Alyssa’s system, doctors said she would be fine.

Samantha, of Bonham Road, Dagenham, said: “Alyssa could have easily died. The boiler is next to her bedroom, so every time I turned on the hot water the gas was going into her room. I feel sick when I think about it.”

The mum-of-one described being frantic with worry when her daughter continued to show symptoms for weeks on end.

“I went to my GP four times and no one could tell me what was wrong with her. I was convinced a child could not be ill that long without it being something serious. I’m so glad that she is OK,” she said.

Samantha said she had felt “tired and achy”, but put this down to caring for a sick child.

Barking and Dagenham Council said boilers in its homes receive a safety check every 12 months and that her boiler was surveyed on May 10. The model was manufactured between 1995 and 2000 and there is no age limit on boilers in council homes.

A council spokesman said: “There has been no previous reports of a suspected gas leak and the first time we were notified was September 19.”

An NHS North East London and the City spokesman said they do not comment on individual cases.