how to stop crawling of https:// urls from google

[mitra]

While checking through the indexed pages of my site, I found lots of
urls with https:// are indexed by Google. It is creating content
duplicity as I found two cached version of the same page, one with http://
and another with https://. I checked for the reason and discovered
that there are some links present in my site with https:// . I can't
stop posting of such urls as I don't have any control over my
visitors.

So my questions are:

1) How do I stop google from crawling the https:// urls?
2) How do I remove the urls that are already indexed with https://?

Please help me with your valuable suggestions asap. I'm in need of it.