Rights holders from across the music and film industries have identified about 100 websites – including The Pirate Bay and "cyberlocker" sites – that they want internet service providers such as BT to block under new measures to tackle illegal filesharing.

Under a voluntary code that is under discussion, content owners would pass evidence of illegal filesharing sites to ISPs, which would then take action against those sites.

However, the proposals are fraught with complications. ISPs are understood to be open to the idea of cutting off access to some infringing sites, but argue that an impartial judge should decide which get blocked. It is also unclear whether content owners or ISPs would be liable to pay compensation to a site that argues that it has been unfairly censored.

The communications minister, Ed Vaizey, is leading a series of talks with rights holders and ISPs, including BT and TalkTalk, aimed at developing voluntary code on internet policy, including site blocking.

The proposal is part of a contentious range of plans to curb illegal filesharing in the UK. Rights holders and ISPs have been at loggerheads over legislation due to be introduced under the Digital Economy Act, which faces a high court challenge by BT and TalkTalk on Wednesday.

BT and TalkTalk – which together have 8.4 million UK subscribers – have already spent close to £1m in legal fees on challenging the act, the Guardian understands. The government, meanwhile, is keen to push through voluntary agreements on controversial issues such as site blocking, as the act faces a delay of at least 12 months.

Issues such as how to give accused sites a fair hearing, indemnity and costs, as well as the governance structure of the code are yet to be ironed out.

"Cheaper than notice sending would be site blocking," said one rights holder present at the government meetings. "We're more interested in site blocking [than mass notification letters]. We don't want to target end users, [the mass notification system] is long winded – we want something now."

Another source at the meeting told the Guardian: "Site blocking is an interesting concept which we're open to, but there are issues on how to make it work, how to give sites a fair hearing, its governance structure and indemnity. But get a judge to tell us to do it and we'll do it."

The culture secretary, Jeremy Hunt, has convened a government-led working group, that comprised ISPs and search engines, to find a "plan B" to avoid potential litigation arising from the blocking of websites accused of illegal filesharing.

The Motion Picture Association (MPA), the trade body representing Hollywood studios including Paramount Pictures, 20th Century Fox and Disney, argues ISPs should block access to filesharing portals such as Newzbin2, The Pirate Bay, Movieberry and Free Movies Online 4 You.

In December, the MPA filed an injunction forcing BT, the UK's largest broadband provider, to throttle users' access to Newzbin2 using the UK Copyrights, Designs and Patents Act. Although the a voluntary set of principles is preferred to the legal route, the high court is expected rule in June on whether BT should block access to the site.