For one side skew you need to use perspective with origin. How ever this method is only usable for an exact size of width and height e.g. 300px and 50px (not usable for sizes by percent).
I have to say that I found +26 degree skew for input by try and error to achieve a good appearance against -30 degree skew of label. You may need to modify these numbers according to the desired width.
label {
width: 300px;
height:50px;
-webkit-transform: perspective(300px) rotateX(30deg);
-o-transform: perspective(300px) rotateX(30deg);
-moz-transform: perspective(300px) rotateX(30deg);
-webkit-transform-origin: 0% 50%;
-moz-transform-origin: 0% 50%;
-o-transform-origin: 0% 50%;
transform-origin: 0% 50%;
display:inline-block;
border:2px solid #323232;
background:rgba(255, 0, 0, 0.3)
}
input {
width:280px;
height:48px;
border:1px solid #ff0000;
outline:0;
-webkit-transform: perspective(280px) rotateX(-26deg);
-o-transform: perspective(280px) rotateX(-26deg);
-moz-transform: perspective(280px) rotateX(-26deg);
-webkit-transform-origin: 0% 50%;
-moz-transform-origin: 0% 50%;
-o-transform-origin: 0% 50%;
transform-origin: 0% 50%;
}
<label><input></label>