Indices Benchmark Correction

IMPAX ASSET MANAGEMENT GROUP PLC

MSCI/Morningstar benchmark correction

London, 10 January 2011 - Impax Asset Management Group plc, ("Impax" or the "Company"), the AIM listed investment manager focused on the environmental sector, would like to provide a revision to the comparable index data for 2008, which corrects a formatting error within today's results announcement.

The benchmark returns in relation MSCI and Morningstar indices for 2008 should have read as follows:

·; MSCI World -17.9%

·; MSCI Small Cap -19.5%

·; Morningstar equity ecology sector average -30.0%

·; Morningstar alternative energy sector average -40.7%

The corrections do not relate to the performance of Impax's strategies.

Enquiries:

Impax Asset Management Group plc

Charlie Ridge, Chief Financial Officer 020 7434 1122

Execution Noble & Co

John Riddell, Director 0203 429 1426

MHP Communications

Gay Collins 0203 128 8582 gay.collins@mhpc.com

07798 626 282