Never! Verbal warnings were abolished in 2009.
At a recent talk I was asked “but can’t we keep using them, if they are part of our policies and procedures?”. The simple answer is yes, but why would you?
Employers complain constantly about the rules they have to comply with. The government removed this “rule”. So why would you choose to keep an extra step in the disciplinary process? Spend time and energy on giving verbal warnings when it isn’t necessary, legally required or even best practice?
The organisations who still have this in their handbooks are unfortunately proving that professionalism is not important to them. Would you still follow a tax law that had been repealed 5 years ago? Voluntarily? No, so why do this?!
Update your processes and find out what rules need to be followed now. Not those from 5 years ago!