Check all the links at google webmasters tool and find out which are spams. Next use disavow tool to remove links.
Where is disavow tool located? Will the Google Webmaster disavow tool remove listing of backlinks in Links to Your Site once it has been listed to remove in disavow tool?
With the help of Google webmaster disavow tool you can inform Google not to consider those backlinks while calculating the Page Rank and search result positioning of your site. Given that, you have already contacted the concerned webmasters and asked them to remove the backlinks to your site. If they don't remove your backlinks even after your request then you can use this tool. You can find better information on this tool here on Webmaster Tool Help: https://support.google.com/webmasters/answer/2648487?hl=en I hope it may help you.