HR asking for payslip is to verify that u r a staff of ur current company and to test ur honesty only...not about salary negotiation (this is what explained by them when i asked them y)......becoz der r still many other benefits which are outside of the payslip that u can create to jack ur expected package (this is from my personal experience, hehe).....

u'll need to sign consent letter in order for the HR to vet on your previous employment (i recently sign one). The HR explained that if you never sign a consent letter and that company does a vet on u, it is deemed illegal for the company.

btw, i have frens working as HR person, they will not disclose on your salary. They will answer yes or no when asked.