The accountant can not be held liable for any amount of tax owed. If something is misreported and it is later determined that you owe more in taxes than what was paid, then you are still the individual who has actual possession of the money that was not paid in, not the accountant. As such, they can't make the accountant liable for a payment of money that he never had control of.
Additionally, it is the taxpayer's responsibility to review the return for accuracy before it is submitted, and to only sign the return if it is accurate. As such, it's extremely difficult to hold an accountant liable for a mistake on a return.
With that being said, you may be able to have him be liable for the interest and penalties that accrued due to his mistake. However, you'd A.) have to file suit against him, and B.) overcome the fact that you signed the return acknowledging its accuracy. I would guess that the penalties and interest aren't large enough to justify the costs and time involved with filing suit, so I think the legal question of your potential success with such a suit is moot.
