US investigators discovered that a suspected Russian spy had been working in the American embassy in Moscow for more than a decade, according to a report Thursday in the Guardian.

The Russian had been hired by the Secret Service and had access to the agency’s intranet and email systems — which gave her access to potentially classified material including the schedules of the president and vice-president, the British paper reported.

The woman had been working for the Secret Service for years before she came under suspicion in 2016 during a routine security sweep conducted by a pair of investigators from the State Department’s security office.

They established she was having regular and unauthorized meetings with members of the FSB, Russia’s principal spy agency.

State shared the information in January 2017 but the Secret Service did not conduct its own investigation, opting to quietly let her go to avoid embarrassment, according to the report.

An intelligence source told the Guardian the woman was dismissed last summer after State finally revoked her security clearance.

Her dismissal came during tit-for-tat expulsions of diplomatic staffers by the US and Russia, a move that provided cover.

“The Secret Service is trying to hide the breach by firing [her],” the source told the paper.

“The damage was already done but the senior management of the Secret Service did not conduct any internal investigation to assess the damage and to see if [she] recruited any other employees to provide her more information.”

The Secret Service downplayed the incident.

“The US Secret Service recognizes that all Foreign Service Nationals who provide services in furtherance of our mission, administrative or otherwise, can be subjected to foreign intelligence influence,” it said in a statement.

“This is of particular emphasis in Russia. As such, all Foreign Service Nationals are managed accordingly to ensure that Secret Service and United States Government interests are protected at all times. As a result, the duties are limited to translation, interpretation, cultural guidance, liaison and administrative support,” it continued.

“At no time, in any US Secret Service office, have FSNs been provided or placed in a position to obtain national security information.”