A mother of twin girls with a rare genetic disorder that leaves them at a risk of brain damage simply for eating too much protein has spoken out in a bid to raise awareness of the condition.

Olivia and Ruby Barnett, both two, from Kingswood have phenylketonuria - known most commonly as PKU - a rare genetic disorder thought to affect between one in 10,000 and and one in 14,000 people in England.

People with PKU are unable to digest the amino acid phenylalanine in the same way most of the population can. Amino acids are compounds that from the basis of protein, and are usually broken down by the body to make our own essential proteins.

The rare condition means that sufferers are unable to break down amino acids, leading to a build up which can cause brain damage.

"You can never, ever take your eye off the ball," mum Leanne said. "Now they are a bit older they want to eat what we have - we have to lock the cupboard doors to make sure that they can't get in and take anything.

"Even something as small as a biscuit is a risk we just can't take. A single slice of bread is half of their daily allowance of protein, so much of what we take for granted is absolutely out of bounds for them.

"When they were babies they've had to drink a special milk formula which essentially gives them exactly the right amount of protein - it tastes and smells absolutely foul and they actually heave when they drink it.

"They have to have a special paste with every meal that they have to take, which they hate and just don't want to go near. Imagine doing that twice over, three times a day, every day, it's incredibly stressful.

"We make almost all of their food from scratch which is hugely time consuming, and the 'free' food which is available on prescription is really hard to get hold of. For example, we've been waiting 14 weeks for a special loaf of bread to arrive."

A 'normal' diet contains around 50 grams of protein per day, however Ruby is allowed just 8.5 grams, whilst Olivia is allowed 8.

Leanne was forced to give up her job with the Department of Work and Pensions in order to keep a close eye on the twins, fearing that a childminder or playgroup may mean Ruby and Olivia are given the chance to get their hands on any food that could take them over their protein limit and potentially cause irreversible damage.

The twins were conceived after 17 years of gruelling IVF treatment, and discovery of their diagnosis just days after birth came as a complete shock to Leanne and her husband Peter, who were thrilled to finally meet their daughters.

"We got a phone call a couple of days after we came home - we were absolutely devestated. PKU is one of the things they screen newborns for, but like most people we had never heard of it.

"All they told us was that they had detected PKU and said that we needed to come straight back into the hospital the following day. They told us not to look PKU up, but when it's your babies of course you're going to look it up. It was absolutely terrifying.

"The only thing I heard at the appointment was that they were going to have to be on a special diet for the rest of their lives, and it was incurable. The rest I just completely blanked, we were so upset that after all this time waiting to have our daughters they were going to have to live this way.

"Bristol Children's Hospital have been incredible and have supported us massively, but you are still left with a lot to research yourself. It was, and to be honest still is, hugely daunting."

Although PKU is a lifelong condition with no known cure there is medication, known as Kuvan, that has been proven to increase a tolerance to protein and help sufferers eat more typical diet.

The drug isn't effective for everyone with PKU, but for those who use it successfully it is proven to significantly improve their quality of life.

At £70,000 per person, per year however, the drug has been deemed too expensive for the NHS, meaning it is not available to anyone in the UK - despite every other country in the EU apart from Poland making it available.

After two years of coming to terms with their daughters' condition, Leanne and Peter have decided to start actively fundraising for the National Society for Phenylketonuria (NSPKU), an organisation which provides vital support and advice to those with the condition, and campaigns for the distribution of Kuvan.

They are holding a disco and raffle event, and have also set up an online fundraising page.

"If it worked, it would absolutely transform their lives," Leanne said. "Their whole lives would just open up in a way that is quite hard to imagine now.

"It would also help us massively as a family, we could go out for dinner together, eat birthday cake, even something as simple as getting an ice cream in the park.

"NSPKU have been an incredible help, anytime you need them you can just go online or pick up the phone for advice.

"We are fundraising because we can't just sit back and let someone else do it for us. These are our daughters' lives, and we will do everything we can to make them as full and as happy as we possibly can."

To donate towards Leanne's appeal, click here.