Impax Asset Management has seen its assets increase by 61 per cent to £7.2bn for the year to 30 September.
The Aim-listed asset manager told the stock exchange this morning that its assets grew by 9 per cent in the last quarter of its financial year.
Its increased inflows do not include those managed by Pax World Management, the acquisition of which Impax announced last month but which remains in the process of being formally completed.
Ian Simm, Impax's chief executive, said: "The 12 months ended 30 September 2017 was the strongest period of growth for Impax since the company’s inception in 1998. We continue to report good investment performance across our strategies and have seen net inflows from European and US clients in all four quarters.
"The acquisition of Pax will diversify our business, create scale for our operations in North America, and broaden the range of investment strategies we will be able to offer our clients, including fixed income and passive equity.
"We expect that the transaction will enhance Impax’s earnings per share significantly in the first full financial year after completion."
The company’s equity funds were the main source of extra inflows with net flows £1.9bn in the year to 30 September.
Impax's private equity funds contributed £155m of net inflows.
The balance of the increased AUM, some £656m, came from performance and currency gains.
Impax’s investments are based on the conviction population dynamics, resource scarcity, inadequate infrastructure and environmental constraints will shape global markets, creating investment risks and opportunities.
It expects these trends, reflecting the transition towards a more sustainable global economy, will drive earnings growth for well-positioned companies.