Dear Sudipto,
In my sixteen years of working life, I had attended couple of interviews. During my second round of interview, some of them asked me salary slips. At that time we were not given salary slips by our company. So I told them the truth. I even told them I could get a salary certificate from my employer. They accepted the reason. Coz, in India, earlier very few companies (that also Ltd. Cos. & not private ltd. co's) used to issue salary slips to their employees. Everyone is aware of this fact. Today the scenario has changed. With the advent of MNCs, every employee is being issued a salary slip. But a few unlucky ones do not get this benefit. Try to talk to your future employer and further produce a salary certificate from your current employer alongwith Form 16, appointment letter, increment letter (if any) and bank statements. This is just for the sake of integrity.
As per your query, whether Form 16 alone is valid as proof of salary, according to me the answer is NO. Form 16 can be fabricated/concoted by any individual, because nobody cross-checks the same. That is why even when you apply for a bank-loan, they ask for Form 16 alongwith 6-months bank statement and pay slips. Hope you have got the answer.8-)