Assets under management were £14.4bn at end-March, compared to £16.1bn three months earlier, with £1.07bn of new money helping to counter a £2.78bn decline in the value of its funds.
Ian Simm, Impax's chief executive, said it was a robust performance given the sharp fall in markets generally.
“Over the three months to 31 March 2020 net inflows were £1.1 billion, a number that includes positive net inflows of £6.0 million during the month of March. The companies that we invest in are generally well established with experienced management teams, diversified business models and strong balance sheets.
“Consequently, over recent months we have had almost no financial exposure to distressed companies," the Impax boss said in a statement.
Simm added that he expects the crisis to increase interest in Impax’s investment strategy and especially companies mitigating and adapting to climate change, reducing pollution and navigating a path towards a more sustainable economy.