The parents of a teenager who died from a suspected drugs overdose at her home in Bromley, south-east London, say that more needs to be done to curb access to websites that mislead vulnerable children with their "gospel of darkness".

Sasha Steadman, 16, who grew up as a member of the youth group at Evangelical Alliance member Bromley Town Church, died on 28 January after being diagnosed with bipolar disorder and suffering bouts of depression.

Sasha was found to have frequented self-harm websites, and blogs on social media site Tumblr that glorified self-harm, suicide and drug-taking, during her illness.

Sasha's parents (mother and stepfather), Claire and Dee Shaw, said urgent action had to be taken to protect vulnerable children, and that sites such as Tumblr should remove content that promotes self-harm.

"It was only after Sasha was diagnosed with bipolar disorder and dropped into fits of depression that she started visiting self-harm websites, we discovered - too late. These sites fed her impressionable mind with their damning gospel of darkness, grooming her to perform what they wanted. They must be stopped," Mr and Mrs Shaw said.

"Laptops and iPads and mobile phones are great devices but they allow a level of privacy which prevents parents from being fully aware."

The couple, along with Christian charity Safermedia, call on social networks to protect vulnerable youth and children by removing malicious content and urge the Government and Internet Service Providers (ISP) to continue introducting ISP-level filters as a matter of urgency.

In a statement Sasha's mother and step father Claire and Dee Shaw said in a statement: "We lost our beloved daughter just five months shy of her 17th birthday, under tragic circumstances. She has left a huge hole in our lives and we are going to miss her terribly."

Sasha is remembered for her joyful creativity, kindness, art and musical talents and was often found daydreaming, singing or dancing. 

Through her illness, different medical professionals were involved trying to help her out of the dark place but Sasha found it difficult to cope.

Adding that some children find it hard to open up, Claire and Dee encouraged parents to create opportunities for children to share and to ensure that they are the first, not the last, port of call when darkness sets in: "We have learnt a very hard lesson, the wounds of which only God, through His grace and mercy, can heal. We don't want other families to suffer similarly, so we appeal to parents to get closer to your children and be involved in their activities. Get to know their friends, their likes and dislikes. If they have a Tumblr account then subscribe to it. If they are on Facebook, be the first to be their friend. On Twitter? Follow them."

"These sites cannot provide help. People are looking for light in a dark place and a way out. We know that this can be appeased through a relationship with Jesus Christ, he is our source of comfort and strength and of hope," they added.

Safermedia stated that they want to see Tumblr and other social networking sites behave far more responsibly and making the well-being of children and teens a top priority above commercial interests.

"They should have the same safeguards in place as off-line forms of the media but instead they are providing frighteningly easy access for children and teens to a wide range of very harmful material that can have devastating consequences," said Safermedia.

"Tumblr must be far more proactive. Last month after being mentioned at the inquest of 15-year-old Tallulah Wilson, they claimed to be 'keeping Tumblr a positive, supportive environment for those individuals dealing with issues of depression and self-harm' but there is little evidence of this so far. If they fail to instigate stricter controls themselves, then there should be some form of enforcement with sanctions."