If you no longer wish for your account data to be available in LastPass, you can delete your account. This will purge all of the contents of your LastPass Premium Vault.
Please see below steps to delete a LastPass Premium account:
1. Go to https://lastpass.com/delete_account.php
2. Click on the Delete button
3. Click No to indicate that you do not know the Master Password.
4. Type in the e-mail address of the LastPass account you want deleted and click Send Email
5. Check your e-mail inbox for the message from LastPass
6. Follow the instructions in the message from LastPass to continue with the account deletion
7. You can recreate the Premium account at https://lastpass.com/partnerpremium/richmond/