The meeting, to brief shareholders on a resolution to be put to next week's annual meeting, has been timed to coincide with the publication by Shell of an environmental report which Pirc has dismissed as "inadequate".
It is the latest move by Pirc to garner support for its controversial resolution, which will call on the company to improve its environmental standards and business ethics policy.
Pirc has been criticised by some fund managers for an apparent shift in its focus from corporate governance issues to environmental matters.
Last week the Association of British Insurers said it would be supporting Shell in its fight against its rebel shareholders at what promises to be a lively annual meeting on 14 May.
Speaking at the meeting will be former Shell executive Sir Geoffrey Chandler, who sits on the board of Amnesty International. He will call on Shell to accept "social auditing" of its human rights performance in order to ensure that Shell's new commitment to the area is verifiable in practice.
Other speakers include Clive Wicks of the WorldWide Fund for Nature which has written to both John Jennings, chairman of Shell International, and Peter Davis, head of the Prudential, the company's largest shareholder, arguing that the insurance company should back the resolution.
In a supporting statement to its resolution, Pirc said: "During the past two years, Shell has faced criticism from shareholders, interest groups and the public over poor environmental standards in Nigeria, associated human rights issues and the handling of the disposal of the Brent Spar platform.
"We believe that these controversies have had an adverse effect on the company's reputation. The effectiveness and consistency of Shell's policies in these issues have important commercial repercussions for the company's global operations."
Pirc said over the weekend that it was too early to say how much support its resolution had but it claimed to have already forced Shell into an intensive lobbying campaign in which it had made presentations to its 50 largest shareholders.
Pirc's resolution, which the lobby group says it has lodged on behalf of a range of institutional clients, as well as religious shareholder groups and private investors, calls on Shell to designate responsibility for the implementation of environmental and corporate responsibility policies to a named member of the committee of managing directors.