The UK Supreme Court has refused to hear the case of a 5-year-old girl whose life support doctors want to turn off.

The courts have repeatedly sided with doctors treating Pippa Knight at Evelina Children's Hospital in London who want to end life-sustaining treatment. 

Her mother Paula Parfitt would like to bring her daughter home on a portable ventilator so she can continue to be cared for by family.

Last month, she lost an appeal against an earlier High Court ruling that said Pippa, who is brain damaged, should be allowed to die. 

Now the Supreme Court has turned down a petition to hear the case. 

John Deighan, CEO of the Society for Unborn Children (SPUC), which has been supporting the case, said Ms Parfitt was "devastated" by the Supreme Court's decision. 

Ms Parfitt, a Christian, is now exploring asylum in Canada where there is a possibility of treatment. 

"She asks that people keep Pippa and her family in their prayers," Mr Deighan said.

"This has been a tremendous effort for the whole family and the legal team who have fought to keep Pippa alive. We have backed this case because we believe that every human life is valuable and worthy of care.

"Paula has been a heroic example of a loving mother and we want to support her. She is right to expect that our society should treasure every person no matter what their condition of health.

"I believe the videos show that Pippa's treatment is not over-burdensome and that she derives great benefit from her mum's care. It is a tragedy that we are powerless before our courts to keep her alive."

Speaking earlier in the case, Ms Parfitt described her daughter as "sweet" and "loving".  

"I know that as a Christian I am a great believer in Gods Law and that is to preserve life. Salvation and creation a must [sic]," she said.

"I am reaching out to the public for their financial support but also for their love, dignity, decorum and strength to resonate, indwell and surround our girl as she is an asset to both Queen and country."