The company has also demanded that the BPI acquire a court order before it will release the identities of the people concerned. Meanwhile the BPI is claiming that Tiscali has supported its actions.
The BPI wrote to Tiscali and to Cable & Wireless demanding that the internet access accounts of 59 people be withdrawn because it said it had evidence that those people were making copyrighted music available online.
While Cable & Wireless pledged to "take whatever steps are necessary to put the matter right", Tiscali said that the BPI had not provided "proper evidence" that offences had taken place.
Both ISPs said that their terms and conditions forbade using the net connection to breach copyright and that the accounts of customers proved to have been doing so would be suspended.
Tiscali's legal response to the request to suspend 17 accounts said: "You state that the evidence is 'overwhelming'. However, you have provided no actual evidence in respect of 16 of the accounts. Further, you have provided no evidence of downloading taking place nor have you provided evidence that the shared drive was connected by the relevant IP address at the relevant time."
It rejects not only the supposed evidence, but also the action proposed by the BPI. It said that the body had demanded that Tiscali identify and suspend the customers in question until both the customers and Tiscali sign a legal agreement with the BPI.
"Tiscali does not intend to require its customers to enter into the undertakings proposed by you and, in any event, our initial view is that they are more restrictive than is reasonable or necessary," said the letter. "It is not for Tiscali, as an ISP, nor the BPI, as a trade association, to effectively act as a regulator or law enforcement agency and deny individuals the right to defend themselves against the allegations made against them."
More extensive evidence was provided in one of the 17 cases, and Tiscali has given that person seven days in which to respond to the allegations, it said.
The BPI released a statement claiming that both Tiscali and C&W back the scheme and that "the BPI can provide full evidence on all 16" alleged file-sharers. "If ISPs do face up to their responsibilities on copyright infringement that has to be good news not just for artists and record companies, but for all the law-abiding music fans who do choose to pay their way," said BPI chairman Peter Jamieson in the statement.