The addition of TCorp to the Australian Council of Superannuation Investors means the group's members collectively manage over $1.5 trillion in assets.
ACSI members also own more than 11 per cent of every ASX200 company, according to a statement by the organisation.
TCorp manages more than $80 billion on behalf of a range of NSW public sector agencies including state-owned corporations and local councils.
"The addition of TCorp reflects the growing diversity of ACSI’s membership," said the statement.
"ACSI was established in 2001 to provide a strong, collective voice on environmental, social and governance (ESG) issues for Australia’s profit to member superannuation sector."
ACSI chief executive Louise Davidson said, "By harnessing our collective rights and interests and actively engaging with boards, we seek to influence the ESG performance of companies, with the aim of promoting long-term shareholder value and minimising risk."
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