Jquery function fires twice on click and not isolated to one of the tabbed boxes

Jquery function fires twice on click and not isolated to one of the tabbed
boxes

jquery function
(function ( $ ) {
$.fn.tabbed = function() {
return this.each(function() {
$("a.tab").one('click focus',function (event) {
event.preventDefault();
// switch all tabs off
$(".active").removeClass("active");
// switch this tab on
$(this).addClass("active");
// slide all elements with the class 'content' up
$(".tab_content").slideUp();
// Now figure out what the 'title' attribute value is and find the
element with that id. Then slide that down.
var content_show = $(this).attr("title");
$("#"+content_show).slideDown();
});
});
};
}( jQuery ));
Html
<ul class="tabs">
<li><a href="#" title="content_1" class="tab active">1</a></li>
<li><a href="#" title="content_2" class="tab">2</a></li>
<li><a href="#" title="content_3" class="tab">3</a></li>
</ul>
<div id="content_1" class="tab_content">
<p>1</p>
</div>
<div id="content_2" class="tab_content">
<p>2</p>
</div>
<div id="content_3" class="tab_content">
<p>3</p>
</div>
<div id="tabbed_box_2" class="tabbed_box">
<div class="tabbed_area">
<ul class="tabs">
<li><a href="#" title="content_4" class="tab active">4</a></li>
<li><a href="#" title="content_5" class="tab">5</a></li>
<li><a href="#" title="content_6" class="tab">6</a></li>
</ul>
<div id="content_4" class="tab_content">
<p>4</p>
</div>
<div id="content_5" class="tab_content">
<p>5</p>
</div>
<div id="content_6" class="tab_content">
<p>6</p>
</div>
</div>
CSS:
#tab_box_1 {
margin: 0 auto;
width: 300px;
}
#tab_box_2 {
margin: 0 auto;
width: 300px;
}
.tab_box h4 {
color: #FFFFFF;
font-family: Arial,Helvetica,sans-serif;
font-size: 23px;
letter-spacing: -1px;
margin-bottom: 10px;
}
.tab_box h4 small {
color: #E3E9EC;
font-family: Verdana,Arial,Helvetica,sans-serif;
font-size: 9px;
font-weight: normal;
left: 6px;
letter-spacing: 0;
position: relative;
text-transform: uppercase;
top: -4px;
}
.tab_area {
background-color: #red;
border: 1px solid #494E52;
padding: 8px;
}
ul.tabs {
margin: 5px 0 6px;
padding: 0;
}
ul.tabs li {
display: inline;
list-style: none outside none;
}
ul.tabs li a {
background-color: #464C54;
background-image: url("images/tab_off.jpg");
background-position: center bottom;
background-repeat: repeat-x;
border: 1px solid #464C54;
color: #FFEBB5;
font-family: Verdana,Arial,Helvetica,sans-serif;
font-size: 9px;
font-weight: bold;
padding: 8px 14px;
text-decoration: none;
text-transform: uppercase;
}
ul.tabs li a:hover {
background-color: #2F343A;
border-color: #2F343A;
}
ul.tabs li a.active {
-moz-border-bottom-colors: none;
-moz-border-image: none;
-moz-border-left-colors: none;
-moz-border-right-colors: none;
-moz-border-top-colors: none;
background-color: #FFFFFF;
background-image: url("images/tab_on.jpg");
background-position: center top;
background-repeat: repeat-x;
border-color: #464C54 #464C54 #FFFFFF;
border-style: solid;
border-width: 1px;
color: #282E32;
}
.tab_content {
background-color: #FFFFFF;
background-image: url("images/content_bottom.jpg");
background-position: center bottom;
background-repeat: repeat-x;
border: 1px solid #464C54;
font-family: Arial,Helvetica,sans-serif;
padding: 10px;
}
#content_2, #content_3, #content_5, #content_6 {
display: none;
}
The jquery is firing twice on click and the box is sliding down twice,
also when either of the tabbed boxes is clicked it is hiding all the divs
on the over tabbed section as well
Anyone come across this before?