Boaz Weinstein’s activist hedge fund Saba Capital Management is maintaining its campaign against one of the UK’s prominent sustainable investment vehicles, putting pressure on the leadership and strategy of Impax Asset Management's Impax Environmental Markets, according to a report by Bloomberg.

Saba, which has built a significant position approaching 30% in the trust, has signalled its intention to remove the current board of Impax Environmental Markets, arguing that long-term underperformance versus benchmarks justifies a change in oversight and direction.

At the centre of the dispute is the management of the trust’s portfolio, long overseen by Impax Asset Management since the trust’s launch in 2002. Critics of the strategy have described recent results as deeply disappointing, with industry commentators pointing to sustained lagging performance relative to broader market benchmarks over a multi-year period.

Impax, however, has defended its position, arguing that the investment case for the trust remains strong and that its sustainability-focused strategy is well placed for future demand.

The confrontation comes at a difficult time for Impax Asset Management, which has seen substantial outflows in recent years alongside a sharp decline in its market valuation from earlier highs. Rising interest rates, sector rotation away from renewable energy, and underexposure to large-cap technology stocks have all weighed on performance and investor sentiment.

If successful, the campaign could mirror earlier actions by Saba involving other UK-listed trusts, where board changes have been followed by attempts to reshape management structures and consolidate assets under a new investment approach.