Police killers are to face minimum whole-life jail terms under proposals to be unveiled by the Home Secretary in front of thousands of rank-and-file police officers.
The current starting point for anyone convicted of the murder of a police officer in the line of duty is 30 years.
But the Government is to propose that this should be increased to a life sentence without parole, Theresa May will tell the Police Federation annual conference.
Mrs May will tell the event in Bournemouth: "To attack and kill a police officer is to attack the fundamental basis of our society.
"We ask police officers to keep us safe by confronting and stopping violent criminals for us. We ask them to take risks so that we don't have to.
"That is why I am clear that life should mean life for anyone convicted of killing a police officer."
The proposals, to be put to the Sentencing Council, will form part of Mrs May's speech before she takes questions from officers on the floor in what is likely to be a heated session.