A TfL spokesperson said: “We are committed to working together with operators to provide a clean environment for staff and customers.
“Most TfL welfare facilities are cleaned multiple times a day, and at a minimum daily, to maintain hygiene and safety standards. All buses are also cleaned every night before entering service and reports such as these are rare.
“We take any report seriously and are urgently investigating the specific incidents that have been raised.
“As with any reports, we will take appropriate action as part of the investigation, which can include taking buses out of service for inspection, deep cleans and treatment with specialist equipment if necessary.
“We would like to reassure staff that our operators would never take action against people raising concerns about welfare or safety and encourage any driver with concerns to contact their employer, their union, or contact us directly.”