Russian police officers had been secretly filming an opposition activist inside her bedroom for months before she was detained and charged under a new law on “undesirable organisations” in a move that has been described as "outrageous."

Anastasia Shevchenko, 40, has been under house arrest for a year after she was slapped with charges related to her work for a civic group founded by Kremlin critic and former oligarch Mikhail Khodorkovsky.

Investigators in the southern city of Rostov-on-Don uncovered footage earlier this month, which showed the single mother of two in her bedroom, her lawyer and family said over the weekend.

Ms Shevchenko’s lawyer Sergei Badamshin posted the court order on social media, showing that police were allowed to bug and film inside her home for nearly five months before she was detained last January.

The police officers had somehow managed to enter the woman’s flat undetected, installed the surveillance equipment and then took it back months later, according to Mr Badamshin: “They left no trace.”