A distraught mother has called for drugs to be legalised and regulated after her teenage daughter died from an ecstasy overdose.

Anne-Marie Cockburn, 43, said she wanted to meet Home Secretary Theresa May to discuss changing the law.

Her 15-year-old daughter, Martha Fernback, died from a cardiac arrest two hours after taking 0.5g of crystallised MDMA, known as ecstasy, in July last year.

Oxfordshire Coroner's Court heard that the schoolgirl, from the Summertown area of Oxford, had taken the drug which was 91% pure - compared to the average street-level purity of 58%.

Ms Cockburn said after the hearing at County Hall in Oxford: "It has been 328 days since my precious girl was safely by my side.

"Martha wanted to get high, she didn't want to die - no parent wants either, but one of those is preferable to the other.

"I wish Martha was sitting her GCSEs alongside her friends at school right now.

"I wish the drug education she received had enabled her to make a more fully-informed decision, instead of leaving her so vulnerable and in danger.

"I would like to meet with Theresa May, Norman Baker and Yvette Cooper to start a sensible dialogue for change, from prohibition to strict and responsible regulation of recreational drugs.

"This will help to safeguard our children and lead to a safer society for us all by putting doctors and pharmacists, not dealers, in control of drugs."

Oxfordshire coroner Darren Salter recorded a conclusion of accidental death.

He said: "It is a terrible loss and I think we can only say that it may at least serve as a warning to young people who may take, or think of taking, ecstasy or MDMA.

"What is clear is that there is no way of knowing what it is made up of or what the purity level is.

"So, as I say, this is a very stark warning of what can happen."

The inquest heard that a friend of Martha's had bought a gram of the crystallised drug and they had split it in half, with Martha taking her share at around midday on the day she died.

The friend, who cannot be identified because of her age, told the hearing in a written statement that she had met up with Martha that morning to go kayaking at a local rowing club.

"We walked and talked and she said to me 'I think I am going to take it today'," the girl said.

"I knew she was referring to MDMA as she had texted me and said 'I think I am going to take it'.

"I knew she had taken it before because I had been with her three times when she has taken the stuff."

The girl said that after kayaking for 30 minutes they had walked into the city centre where Martha had swallowed the drug with water.

"We walked past a school and she said it was kicking in and we were joined by a friend of ours," the girl said.t

"About 20 minutes after she had taken it I could see that she was high.

"I kept asking what it felt like and she said things like 'It's amazing, it feels like a dream - it's better than the last time we did it'.

"Her pupils were dilated and her jaw was shaking like she was cold.

"We were now on the High Street in Oxford and Martha kept on walking ahead and borrowing our friend's phone.

"She kept going through his contact list and phoning people and saying 'I've just taken half a gram and it's amazing'.

"She kept sitting down like she was tired and was acting strangely.

"I now realise Martha was sweating a lot and overheating. I said she should drink some water as she looked really hot. She drank some water and we carried on walking.

"We met up with another friend of ours and Martha was still acting weird and complaining about how far it was to walk."

The girl said they walked to Hinksey Park where they were joined by another friend and the five-strong group sat on a bench to eat some food they had bought earlier.

The hearing heard that Martha said she wanted to go swimming at the nearby open air pool in order to cool down and as she stood up she fell down - banging her head on the ground and causing it to bleed.

"I remember her being limp and falling," the girl said.

"The others came over and helped me hold her and we got her back to her feet. I said to her 'Are you okay?' and Martha replied 'I'm okay' but I could see her eyes rolling backwards.

"We moved her back to the bench and she lay down and I could see her lips were going blue and she went really pale.

"I kept saying 'Can you hear me Martha, are you okay?' Martha wasn't responding and I told one of our friends to call an ambulance.

"I was panicking a bit now and so were our friends."

Another friend said he met Martha and her female friend in the city centre after she had taken the drugs.

"Martha started to tremble and started shivering," he said.

"I wasn't too keen to be around Martha so I texted my friends and told them she was becoming difficult to handle.

"Martha's behaviour started to get worse and she wanted to go into the shops and was drawing attention to herself.

"We decided it would be better to go to Hinksley Park and sit by the lake."

He added: "Within seconds Martha went very pale and she was struggling to breathe. She was trembling uncontrollably and Martha collapsed into me and my friend.

"I then noticed blood over me and my friend, which was coming from Martha's head.

"We put her on the floor and tried to sit her up. Martha started to wheeze in her breathing. She collapsed and stopped breathing and we all panicked."

They alerted staff at the swimming pool who ran over and started trying to resuscitate the teenager.

The boy said he rang Martha's mother to tell her what had happened and said they had called for an ambulance.

The emergency services quickly arrived and Martha was taken to hospital where she was pronounced dead an hour after first collapsing.

A post mortem examination concluded that Martha had died as a result of MDMA toxicity having suffered a cardiac arrest.

Pathologist Dr Nicholas Hunt told the hearing: "The MDMA concentration was very high and well within the reported range where deaths have been attributed to an overdose of this drug."

The inquest heard that the person who had supplied the drugs to Martha and her friend had been prosecuted.

Members of the schoolgirl's family attended the hearing, including Ms Cockburn, Martha's father Sean Fernback, 50, and Martha's grandmother.

Since her daughter's death, Ms Cockburn has set up a website, called What Martha Did Next.

Ms Cockburn, a marketing consultant, has also written a book called 5,742 days - the number of days Martha lived - that she wants to see in all secondary school libraries to "open the eyes" of young people to the dangers of drugs.

Crime Prevention Minister Norman Baker said: "All drug-related deaths are tragic and my sympathy goes to Martha's mother.

"The UK's approach on drugs remains clear: we must prevent drug use in our communities, help dependent individuals through treatment and wider recovery support, while ensuring law enforcement protects society by stopping the supply.

"It is encouraging that drug use has fallen to its lowest level since records began in 1996. However, we do not assume that we have nothing to learn from others, which is why we are conducting an international study to examine the approaches other countries are taking on drugs."