Aid group Médecins Sans Frontières says a soon-to-be-sealed trade deal will not only push up local medicine costs, but place life-saving ones out of reach for millions of patients in developing countries.

At a public forum organised by critics of the Trans-Pacific Partnership on Thursday, Médecins Sans Frontières Australia's advocacy manager Jon Edwards said leaked chapters showed it granted pharmaceutical companies extended patents, allowing them to charge higher prices.

Trade Minister Andrew Robb is negotiating the Trans-Pacific Partnership. Credit:Reuters

The regional trade pact, which involves 12 countries covering 40 per cent of the world's economy, has also come under fire for containing a clause that allows multinationals to sue governments if new laws harm their profits.

A late-stage draft of the Investment chapter, leaked in March by Wikileaks, showed some public health carve-outs, specifically the Pharmaceutical Benefits Scheme, Medicare Benefits Scheme, Therapeutic Goods Administration and the Office of the Gene Technology Regulator.