Try it from server side using htmlencode. It will work.
<pre lang="c#"><asp:radiobutton id="RadioButton1" runat="server" groupname="f1" xmlns:asp="#unknown" />
protected void Page_Load(object sender, EventArgs e)
{
string button = "<input type=button value=Search name=btnSearch />";
RadioButton1.Text = Server.HtmlEncode(button);
}