My experience with this was in London, a twitter.com recruiter contacted me a couple of years ago. At the time I was searching for a job so I replied that I was

My experience with this was in London, a twitter.com recruiter contacted me a couple of years ago. At the time I was searching for a job so I replied that I was interested. We had the usual HR/Recruiter call. It ended with them asking how muh my previous employer was paying me. I said that was confidential and would not share. Their reply was "this information is mandatory and we cannot continue the process if you will not provide it." I said I wouldn't and it ended there... two months later their recruiter contacted me again saying it was ok for me not to share and provide expectations instead.