The investigation will examine how and why this situation has happened, and identify possible solutions.
Monitor granted St Georges foundation trust status in February 2015 on the basis it would break even in 2014-15 and make a small surplus in 2015-16. The regulator is now concerned as the trust has recorded a 16.8 million loss for 2014-15 and may record a larger deficit in 2015-16.
The regulator also wants to understand why St Georges has failed to sustain its progress in treating patients more promptly, as requested at the time of its foundation trust authorisation.
Monitor will announce the outcome of the investigation in due course.