Get the chair of your department and the appropriate dean(s) involved. They will help you begin a process that will (or could) end up with the student being removed from the program. Deans and Chairs know how to do this properly, with paper trails and specific goals and documentable targets that the student will have to achieve in order to continue in the program.
Probably you'll end up sitting down with the student, the advising committee, and the Chair, and set a series of specific things that the student will need to do, by specific dates, in order to stay in the program. Document the goals, and set them to be realistic and achievable by a good student -- in other words, you can't set the student up to fail with impossible goals, but it's fine if the goals are impossible for them; that's the point, that they can't achieve reasonable goals.
Make sure the student is aware that they need to meet these goals or they are out.
Document, document, document. Record the progress the student has made so far and what they have failed to achieve. Hold weekly meetings with the student and note progress, or lack of it. If after six months (or whatever the committee recommended) the student has not met the goals, don't revise the goals or say "Oh, pretty close, we'll give you another two weeks". If the student didn't meet the goals you agreed on, they should be out of the program, and this is not something you can do, it's up to Deans and administrators, so you need to be communicating with them throughout.
If the student does achieve the goals, set a new series of goals for the next six months with exactly the same documentation and aims.
The most likely thing that that the administration will find a moderately face-saving solution for everyone involved. Most often, the student will be given an option to "Master out" -- everyone will agree that they've met the qualifications for a Master's degree, not a Ph.D., here's your diploma, good luck, don't let the door hit you on the way out.
Does this sound like a lot of work? Probably -- but it's not much more than you should be doing for all your students anyway. Setting goals, holding meetings to ensure progress, holding people accountable for their actions and progress, are all routine processes for managers, which is what you are (among many other things). Unfortunately most academic supervisors aren't trained in management and have to learn it the hard way, screwing up at least one student's life and their own in the process.