diff --git a/lib/Cleantalk/Antispam/Integrations/SimpleMembership.php b/lib/Cleantalk/Antispam/Integrations/SimpleMembership.php
index a03785e16..4ae20a143 100644
--- a/lib/Cleantalk/Antispam/Integrations/SimpleMembership.php
+++ b/lib/Cleantalk/Antispam/Integrations/SimpleMembership.php
@@ -29,12 +29,53 @@ public function doBlock($message)
         global $ct_comment;
         $ct_comment = $message;
 
+        $wp_user = ! empty($this->member_info['email'])
+            ? get_user_by('email', $this->member_info['email'])
+            : false;
+
         if (class_exists('SwpmMembers') ) {
             $member    = \SwpmMemberUtils::get_user_by_email($this->member_info['email']);
             $member_id = $member->member_id;
             \SwpmMembers::delete_user_by_id($member_id);
         }
 
+        if ( $wp_user instanceof \WP_User ) {
+            $this->deleteUserFromNetwork($wp_user);
+        }
+
         ct_die(null, null);
     }
+
+    /**
+     * On multisite wp_delete_user() only detaches the user from the current site,
+     * so the blocked registration still shows up in Network Admin -> Users.
+     *
+     * @param \WP_User $wp_user
+     *
+     * @return void
+     */
+    private function deleteUserFromNetwork(\WP_User $wp_user)
+    {
+        if ( ! is_multisite() || is_super_admin($wp_user->ID) ) {
+            return;
+        }
+
+        // Keep the account if it is still attached to any other site of the network
+        $blogs = get_blogs_of_user($wp_user->ID, true);
+        unset($blogs[get_current_blog_id()]);
+        if ( ! empty($blogs) ) {
+            return;
+        }
+
+        // Only the account created by this very registration may be removed
+        if ( strtotime($wp_user->user_registered) < time() - 300 ) {
+            return;
+        }
+
+        if ( ! function_exists('wpmu_delete_user') ) {
+            require_once ABSPATH . 'wp-admin/includes/ms.php';
+        }
+
+        wpmu_delete_user($wp_user->ID);
+    }
 }