Removal of unwanted phone extension cable

[HammerHead100]

Hello!
This wire leaves the BT master socket box and goes to an extension that's no longer used. Can I just snip this wire? What I want to avoid is:
a) electrocution
b) losing my internet connection / landline
Thanks for any help.

 

[Sureitsoff?]

you could but a better way would be to take the socket of the wall and you will see where the extension wiring is connected to. then carefully cut each individual wire as close to the connection as possible ensuring that any of the bits from the cut cable left in the connection block dont touch each other then put the socket back on the wall.