An 80-year-old woman who gave her terminally ill husband a fatal dose of medicine so he could end his life has been cleared of murder, triggering calls for a change in the law on assisted dying.

Mavis Eccleston and her 81-year-old husband, Dennis, formed a pact to end their lives together, Stafford crown court heard. She said she gave him the medicine, which he took himself, kissed him and pulled a cover over him. He kissed her hand and said “Good night darling” as Eccleston, who had also taken the medicine, went to lie down on a sofa.

The couple had been married for 60 years. Dennis was suffering from advanced bowel cancer and had talked of ending his life.

They were found at their home in Huntington, near Cannock, Staffordshire, in February last year and were taken to hospital where Eccleston, who survived, was given an antidote.

In the final hours of Dennis’s life, hospital staff pulled their beds together. They held hands as he died.

The couple wrote a note to their children explaining their decision.

The prosecution had claimed Eccleston told hospital staff her husband did not know the medicine would end his life, a claim she denied.

The jury took four hours to return not guilty verdicts on charges of murder and manslaughter.

During the two-week trial Eccleston said she took the medication from a cupboard and gave it to her husband. “It was an understanding between us. He had to tell me what I had got to do.”

After the verdicts, the couple’s daughter Joy Munns, 54, called for the law on assisted dying to be reformed. “We do not believe this needed to happen. If there had been an assisted dying law in the UK, our dad would have been able to have the choice to end his suffering with medical support, and with his loved ones around him.

“Our dad would have been devastated at the thought of his beloved wife waiting to find out if, at the age of 80, she would face a life sentence in prison simply for respecting his wishes.

“He would have been heartbroken if he had known his wife and family would have had to endure 18 months of extreme anxiety and distress.

“We believe there must be a change in the law so that dying people aren’t forced to suffer, to make plans in secret or ask loved ones to risk prosecution by helping them.”

Sarah Wootton, the chief executive of the campaign group Dignity in Dying, said: “Dennis ... simply wanted to die on his own terms rather than endure a protracted, painful death, but because of the UK’s outdated laws on assisted dying, Dennis felt his only option was to end his own life behind closed doors.

“Mavis, his devoted wife, felt she had to respect his wishes, but then faced the prospect of life imprisonment simply for acting out of love. Compassion should not be a crime, but under the UK’s broken laws, it is.”