Elon Musk has indicated that a verified account on Twitter in the future will cost $8 a month, despite facing a user backlash over proposals to charge for the feature.

The new owner of Twitter described the current system for allocating blue check marks – which verify a user as a trustworthy source – as “bullshit” in a Twitter post to his more than 110 million followers on Tuesday.

In the Twitter thread, Musk said subscribers to the new Blue service would also get priority in replies, mentions and search, which he said was “essential to defeat” spam accounts. Users will also see half as many adverts and will be able to post long video and audio clips. No timing for the changes was announced.

The changes would affect about 400,000 blue tick accounts on Twitter. Advertising, which would be reduced for Blue subscribers under the plans, accounts for 90% of Twitter’s $5bn in annual revenue.

Hours before, Musk justified his plans to charge for verification by tweeting that “we need to pay the bills somehow”, adding that it was the only way to “defeat the bots and trolls”. Musk made the comments in an exchange with the author Stephen King, who had tweeted that if a $20 tick-charge were implemented “I’m gone like Enron.” “How about $8?” Musk responded.