BT (NYSE: BT) appears to have joined Virgin Media (NSDQ: VMED) in sending warnings to its customers whom the British Phonographic Industry (BPI) says are illegally sharing music. One such customer told The Register she got a cease-and-desist email with evidence collected by the BPI that she had “offered” Girls Aloud’s Biology ( play here) using the Ares P2P app last month.

Like the letters Virgin Media recently began sending out in its “education campaign” on the BPI’s behalf, BT’s warning includes touchy-feely customer advice about ensuring network security. But BT’s addition is significant - it’s the UK’s biggest broadband supplier. BPI CEO Geoff Taylor said he is “forming positive working relationships with BT, Virgin Media and most of the other major ISPs”.

These ISPs are trying to work together with the music biz before the government next April imposes a measure such as France’s three-strikes policy. In Portugal, meanwhile, there is a different last-ditch attempt. A court has jailed a man for 90 days to “set an example” after he was found to have illegally shared tunes online in a case brought by the Portuguese Phonographic Association - the country’s first such sentence for the crime, The News reports.

• Virgin, BPI Send Users Piracy Letters In ‘Education Campaign’
• Music Industry Takes Anti-Piracy Scare Tactics To Schools
• ISPs Given April 2009 Deadline To Implement Anti-Piracy Processes