A potentially dangerous Request.Form value was detected from the client error. That's because lname field has html content lname="Test"

Question

I am using captchaMVC and on IsCaptchaValid("") I am getting A potentially dangerous Request.Form value was detected from the client error. That's because lname field has html content lname="<p>Test</p>" How can I fix this error

            [ValidateInput(false)]   
            [HttpPost]
            public ActionResult Index(FormCollection dataColl)
            {
                Test datgrp = new Test();
                datgrp.fname = dataColl[0].ToString();
                datgrp.lname = dataColl[1].ToString();

                if (!this.IsCaptchaValid(""))*****//ERROR IS HERE*****
                {

                    ViewBag.Classname = "alert alert-warning";
                    ViewBag.ErrorMessage = "Incorrect captcha answer.";
                }
                else
                {
                    ViewBag.ErrorMessage = "OKAY";
                    return RedirectToAction("Index", "Home");
                }

                return View(datgrp);
            }