The RSPCA is urging the UK government to ensure that the deal with Australia includes non-regression clauses on animal welfare.
As the UK announces a deal with Australia agreeing tariff-free imports of beef and lamb by 2036, risking imports produced to lower animal welfare standards than those permitted here, the RSPCA warns that it could set a damaging precedent.
The animal charity is urging the UK government to ensure that the deal includes non-regression clauses on animal welfare and safeguards against beef coming into the UK that has been injected with hormones when agreeing terms.
Supermarket shelves could soon be stocked with food from countries with much lower welfare standards than the UK.
Examples include imported beef from cattle raised on enormous, bare feed-lots and suffering transport times of up to 48 hours, pork from pigs that have been forced to breed in restrictive sow stalls, or chlorine-washed chickens raised under filthy conditions.
Concerningly, as the UK's procurement standards allow in low welfare imports, these products could even find their way onto the menus of public sector organisations and into the meals of school-children and hospital patients.
Cheap low quality imports could also undercut farmers and, if more trade deals follow suit, devastate the UK's farming industry.
RSPCA Chief Executive Chris Sherwood said: "We are concerned to hear that a tariff free deal has been done on beef and lamb and need reassurance that there will be equivalence to our standards on any imports in the deal. So we now urge Boris Johnson to take every step he can to safeguard animal welfare with the details of the agreement.
"As our first trade agreement since leaving the European Union, it is really vital the government gets it right and ensures our welfare standards are safeguarded or it could give a clear signal to other countries that the UK's international trade policy has no red lines when it comes to upholding animal welfare standards.
"In Australia it is legal to mutilate the rear end of sheep, sometimes without anaesthetic. Egg laying hens are kept in battery cages and chicken can be washed with chlorine. Cattle may never see a blade of grass and almost half the herd are given growth hormones."
"Unless a high bar bar can be established now, UK trade negotiators' hands will be tied when they try to clinch higher welfare deals with other priority countries such as the USA, Canada, Brazil and Mexico, all of which have lower animal welfare standards than the UK.
"The UK should be proud of its animal welfare standards and strive to maintain and improve them, but there's a danger this is being sold out for the sake of a quick trade deal."