After triumphing in a five-way pitch, the agency has been charged with positioning the hotels as an iconic part of London culture.
Exposure CEO Raoul Shah said: ‘St Martins Lane and Sanderson are much-loved, iconic London destinations. They made the hotel lobby the place to hang out and set the benchmark for bars and restaurants across London today.
'We are excited to be working with the team at Morgans Hotel Group, and look forward to keeping both hotels at the forefront of London culture.’
Comms duties for both hotels were handled previously by Purple PR, which will continue to handle PR for the Morgans Hotel Group's international brands and Mondrian London, due to open in 2014.
The hotelier also operates boutique luxury hotel brands the Delano, Mondrian and Hudson in locations such as Los Angeles, New York, Miami and Marrakech.