Bill Shorten is preparing to unveil a major new economic policy as soon as next weekend which could raise billions of dollars for the budget and rival the party's bold negative gearing and capital gains tax crackdown in terms of political risk.

Senior Labor figures were tight-lipped on Friday about what the new tax policy will be but Fairfax Media understands it could be signed off by shadow cabinet next week and has been pencilled in for an announcement at the NSW Labor Party conference on July 29.

The move signals Mr Shorten's willingness to take on the Turnbull government over the politically fraught topic of tax, rather than play it safe and attempt to preserve Labor's commanding lead in the opinion polls.

Mr Shorten dropped hints during a speech in Melbourne on Friday, saying Australia must examine the "old and growing faults" in the tax system and pursue "reforms that in the past we might have dismissed as too politically difficult".