ITV News has uncovered doubts over how qualified Victorino Chua was before he came to the UK and poisoned patients.
Before he came to the UK in 2002, the father-of-two was trained at Galang Medical Centre, which was rated as the "worst nursing school in the Philippines" and forced to close in 2000.
"Nobody wanted to go to Galang for treatment. It had a bad reputation, There were students who did not complete their training and it was common knowledge they bought their qualifications," one resident said.
ITV News has discovered how easy it is to purchase fraudulent nursing qualifications in the capital Manila to be used in the UK.
A secret buyer was able to purchase the documents for just £75 and five hours after the order was placed, the buyer was a qualified nurse on paper.
Asked whether action was needed to crackdown on the practice of buying papers, Carmelita Divinagracia, who works for the country's nursing regulator, told ITV News: "Yes definitely. We are moving heaven and earth because it is going to affect the nursing profession."