Asp.net label returns empty string when using jQuery [Visual Web Part]

I have created a SharePoint 2010 visual web part. In the page load event of the user control, i am setting the value of an asp.net label.

<asp:Label ID ="lbMessageIndex" runat="server" Visible="false"></asp:Label>

protected void Page_Load(object sender, EventArgs e)
        {    
           lbMessageIndex.Text = "0";                
        }

I also have a anchor tag with a click event getLabelValues() . In this method, when access the label value using jQuery, empty string value is returned.

function getLabelValues() {
        var index = $('#<%=lbMessageIndex.ClientID%>').text();
        alert(index);
    }

Note - .html() and .val() returns undefined.