<a href="<?php echo $this->url('agency', array('action'=>'showform', 'controller'=>'agency')); ?>" role="button" class="btn btn-primary" data-toggle="modal"  data-target="#formpopup" >Add Agency</a>

<!-- empty modal div to hold content that is loaded via AJAX -->
<div id="formpopup" class="modal fade" role="dialog" tabindex="-1" aia-labelledby="myModalLabel" aria-hidden="true">
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
                <h4 class="modal-title">Modal title</h4>
            </div>
            <div class="modal-body">
              ...
            </div>
            <div class="modal-footer">
              <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
              <button type="button" class="btn btn-primary">Save changes</button>
            </div>
        </div><!-- /.modal-content -->
    </div><!-- /.modal-dialog -->
</div>