Unpaid tax deducted at source

I perform business support services. For the period April - October 2013 one of my clients has deducted Income Tax at Source (TDS) at 10% of the fee charged (including on the service tax portion). However I find from my Form 26AS that the TDS amount has not been remitted against my PAN. My queries with the client remain unanswered. Am I liable to pay the tax deducted? What action can I take?