I have started declining to tell my current salary. I explain that my offer should be related to the value I bring to the company, not based on previous work at another company.
I went through a screening process a couple of years ago with an enterprise level company. A recruiter reached out to me about a position that looked appealing to me. One of my first questions to the recruiter was the salary range for the position. It was right in line with what I was expecting, and I replied that the range was satisfactory.
During the phone screen (done by the recruiter, not the hiring manager), I passed all of her questions. Towards the end she had some background questions, including my current salary. I explained that I was unwilling to divulge that information, but that I found the agreed salary range to be acceptable.
The recruiter explained that she could not continue the screen without that information. When I explained that I declined again, she hung up on me.
Since then I have spoken to other people that work for the company, and they have nothing good to say about working for the company. So I guess my policy paid off.