UK employers must automatically enrol their staff into a workplace pension if they meet certain criteria. The law on workplace pensions has now changed and every employer must comply.
Visit http://www.thepensionsregulator.gov.uk/employers/e-brochure/index.html to access The essential Guide to Auto-enrolment.
http://www.thepensionsregulator.gov.uk/employers/tools/staging-date.aspx