A CPS spokesperson said: “In light of further evidence received by the CPS we have arranged for the discharge of the European Arrest Warrants (EAWs) in relation to Brett and Naghmeh King.
"The CPS has urgently reviewed the case and we consider there is insufficient evidence for a realistic prospect of conviction for any criminal offence. We have therefore decided to stop the criminal proceedings.
“When the EAWs were first issued, at the request of Hampshire Police, on Friday 29 August, the evidence indicated that there was a likelihood that this five-year-old boy was at serious risk of threat to his life, and that he could not receive the care that he required unless he was under the care of medical professionals.
“Ashya King had major surgery to remove a brain tumour five weeks ago, and a further operation on his brain on 22 August.
"As a result of these procedures he was extremely ill and has been unable to speak and unable to eat or drink on his own.
"The evidence was that he required round the clock nursing care to manage his recovery, including to manage the feeding tube which was keeping him alive and hydrated.
"This feeding tube can easily become dislodged and, if not handled correctly, can cause a serious risk to health. It was evident that Mr and Mrs King had not had the necessary training to remove it and reinsert it if it had become dislodged.
"If this happens, the food can enter the lungs which can be fatal. The evidence was that the King family also did not have any of the specialist nutrition that Ashya needed and that the feeding tube required charge from a battery which was running out and for which the parents had not taken the power supply.
"There was a reasonable suspicion that Ashya’s health and safety were likely to be seriously harmed if he was not returned to medical care urgently.
“The information was from medical professionals who were extremely worried that a child was in real danger and that, as a result of being removed from Southampton General Hospital and taken abroad without a medical plan for treatment and care, this seriously ill little boy would not get the care that he desperately needed.
"Therefore the CPS was asked to consider if there was a reasonable suspicion that Mr and Mrs King had committed an offence of child cruelty through wilful neglect.
“Today has shown that Mr and Mrs King did take certain steps to safeguard the health of Ashya, for example it appears they had ordered specialist foods to care for Ashya, and had managed to charge the food pump using their car battery.
"Also, evidence from two independent medical experts indicated that the risk to Ashya’s life was not as great or immediate as had been originally thought.
"Accordingly the necessary element of wilful neglect to support a charge of child cruelty could not be proved to the required standard.
“Some of this evidence was received by the CPS today, and we have acted as quickly as we could to take the necessary steps to release Mr and Mrs King from custody as soon as possible.
"We continue to work with the UK courts and Spanish authorities to progress matters as quickly as possible.”