Why my power adapter is giving me electric shocks?

I have a Dell Inspiron N5110. (6GB RAM/2nd gen i5). Bought it in late 2011. A very good laptop for majority of my needs. Have used it extensively. After battery died completely it was sitting idle for a while. Since last year I started using it again as a desktop PC connected to the power supply coming from our power backup UPS. So unforseen power outage and immediate shutdown wasn't an issue. It did happen couple of times as i tripped on adapter cable. Clumsy me. But other than that nothing else. It was working fine. My adapter is still working. It powers up the laptop. But yesterday i tried to pickup the adapter brick as system was powered on and it gave me a very strong shock. I used a voltage tester and it shows that there is electrical current all around the brick along the line where both casings of the adapter brick meet each other. Not only that, current is also present at the joint of the brick from where cable leaves for laptop port, current is literally flowing through protective insulation of wire at that joint. Why? And what do I do? Shoud I replace adapter or just use electrical tape and cover it up? Also can I continue using laptop without battery with new adapter? I want to get new laptop in a couple of months but not immediately. So don't want to spend on a new battery unless it's needed badly.