Users of the Covered California website, attempting to sign up to the scheme before the 31 March deadline, were given the option of calculating the cost of health coverage, including a line for those with hearing impairments.

But the number listed was wrong by one digit, CBS Sacramento reported, and did not connect to the insurance company.

“Welcome to America’s hottest talk line. Ladies, to talk to interesting and exciting guys free, press one now. Guys, hot ladies are waiting to talk to you. Press two to connect free now,” the recording on the adult chat service said.

One resident said he logged on to Covered California’s website, and having filled in his information, was prompted to call the company’s helpline. When he was taken to the adult service, he redialled, but soon realised the number was wrong, the US network reported.

The mistake has since been fixed on the Covered California website.

A spokesperson from Covered California told the US network that the issue was isolated and only appeared under certain circumstances, but did not elaborate.

The incident came a day before US President Barack Obama hailed his healthcare legislation, nicknamed Obamacare, a success after 7.1 million people had signed up for the coverage.

About 50 million Americans lacked health care coverage as the law began taking effect, and supporters hope it will significantly reduce the ranks of the uninsured.

Republicans have bitterly opposed the law, but many Democrats hope it will be regarded as a defining moment in Obama’s presidency.

The months ahead will show whether the Affordable Care Act will meet its mandate to provide affordable health care coverage, and if any other bureaucratic gaffs will emerge.