Judicial Watch, a conservative watchdog group in the US, has said that the former Secretary of State Hillary Clinton used an unsecured phone line when the secure line was experiencing technical issues. The group said she directed a top aide to call her on her home number.

“I give up. Call me on my home [number],” Clinton told then-Chief of Staff Cheryl Mills in a February 2009 e-mail after more than an hour of trouble trying to communicate via a secure line. “I just spoke to ops and called you reg line — we have to wait until we see each other b/c [the] technology is not working,” Mills said in another e-mail sent at almost exactly the same time. “Please try again,” responded Clinton, a few moments later.

It’s unclear whether the two did connect or if they moderated any discussion they may have had to avoid sensitive topics while on an unsecure landline.

But the episode is likely to cause concern among critics of Clinton, who have previously accused her of resorting to unsecure forms of communication out of convenience, potentially jeopardising sensitive information. Another e-mail of Clinton’s, released in January, appeared to show her telling a top aide to remove identifying details and send a sensitive document through a ‘non-secure’ channel instead of via ‘secure fax.’

“This drip, drip of new Clinton e-mails show Hillary Clinton could not care less about the security of her communications,” said Tom Fitton, the President of Judicial Watch, in a statement.