A landmark paper by bank economists Will Martin and Aaditya Mattoo estimates that an agreement along the lines that appear possible would cut average farm tariffs globally from 14.5pc to 11.8pc, and average manufacturing tariffs from 2.9pc to 2.3pc.

Australia would make the biggest cuts proportionally, they estimate, with its average manufacturing tariff slashed from 3.6pc to 2.4pc — at odds with government statements that only small areas of the vehicle and textile, clothing and footwear sectors would be affected.

They warn that the "flexibility" built into the draft texts in both the main streams of the negotiations would largely negate the headline-grabbing numbers for tariff cuts waved around by negotiators.

Further, in agriculture, the World Trade Organisation negotiations are about cuts in bound tariffs — the levels that countries commit to hold tariffs below — and not actual tariffs, which are typically much lower.

Dr Martin, an Australian, and Dr Mattoo emphasise that the kind of agreement that now seems possible would still deliver real benefits — by improving market access and by sharply lowering the ceilings, reassuring exporters that markets will not be suddenly shut off.

"However, given the large gaps today between legally bound and actually applied levels of protection, the reductions in bound levels of protection will lead to much smaller reductions in currently applied levels of protection," they conclude.

In agriculture, for example, the rich countries on average would agree to more than halve their bound tariffs, from 32pc to 20pc.

But their actual tariffs average just 15pc, and assuming they use their flexibilities to protect their most vulnerable areas, that would fall just to 11pc.

Developing countries, which would be given even more flexibility, would mostly be able to avoid making tariff cuts.

In manufacturing, the rich countries have tried to raise the bar by demanding cuts in actual tariffs rather than bound ones.

But to get there, they have had to concede flexibilities that would roughly halve the impact.

Developed countries would have to cut their average tariffs from 1.7pc to 1pc.

The poorest developing countries would not have to make cuts, while the middle-income developing countries such as China would cut their average tariffs from 6.4pc to 5.6pc.