Vanguard has allegedly prevented climate partners from joining its annual institutional investor webinar. 

Even though their registration for the session was first approved by Vanguard, Sierra Club was obstructed from attending the session, the grassroots environmental organisation claims.

When attempting to join the 12 January webinar, Sierra Club's access, along with other climate organisations, was blocked without explanation, according to Jessye Waxman, senior campaign representative at Sierra Club.

Waxman tweeted: "Vanguard is currently hosting its annual webinar for institutional investors. Sierra Club & other climate partners have been blocked from that meeting".

"It's notable that on the retail investor call earlier this week, Vanguard did not speak about climate change or climate risk mitigation...Also a notable oversight because Vanguard left the Net Zero Asset Managers Initiative last month".

The passives giant exited the Net Zero Asset Managers initiative (NZAM) in early December last year, and said: "After a considerable period of review, we have decided to withdraw from NZAM so that we can provide the clarity our investors desire about the role of index funds and about how we think about material risks, including climate-related risks - and to make clear that Vanguard speaks independently on matters of importance to our investors.

"This change in NZAM membership status will not affect our commitment to helping our investors navigate the risks that climate change can pose to their long-term returns."

Vanguard had not responded to Sustainable Investment's invitation to comment at the time of publication.