How can I cut benefits, not engagement?

The problem I am a benefits and rewards manager working in the private sector. The recession and ongoing economic uncertainty has had a huge impact on my work; my budget has been slashed and I need to cut back on my benefits spend quickly. For many years our employees have enjoyed a healthy, creative, flexible benefits pot that we have been able to regularly update, alongside a generous core benefits offering. How can I cut back on what we offer our people without having a devastating effect on our employer brand and staff engagement levels, as well as our relationship with benefits providers?