It's a dificult thing to do but you or another collegue, with the backing and support of the rest of the staff realy need to explain calmly, sensibly and civaly that they are distracting everyone. Something along the lines of 'Would you please be quite as we need to concentrate' may be enough. If no-one does anything it will only get worse and worse and ill feelings will start to cloud the issue. Get it over and done with quickly.

I had to sack someone once. I kept putting it off until in the end it was realy stressing me out. When I finaly did it I was a nervous wreck and she just responded with 'OK - I was not realy happy anyway'. Could have saved myself weeks of stress.

Hope this helps

Cheers

DtG