well, all this while i have been working, the HR has been asking my previous company payslip. I think is mostly to make sure the figure that the figure I put in the resume are tally. Also to check if the candidates are telling the truth. If the headhunter or recruiter ask for the payslip, just say NO. They are not suppose to see your payslip anyway except for the company HR that is hiring you.

To me, i don't think is any wrong for the current HR to know your previous last drawn salary. Furthermore, that salary is the past. More concerned would be the current salary drawn.

For the bargaining issue, most HR will actually check for the last drawn salary and and hike the salary from there. But there are some exceptions like:
i) market rate
ii) job responsibility
iii) job grading ( like gov sector, banking sector and etc)

TS, you can use the above to justify you expected salary. but nevertheless, don't go overboard.
good luck.