The UK’s flagship trade deal with Australia “is not actually a very good deal” for the UK, former government minister George Eustice has admitted.

Speaking in the House of Commons on Monday, the Conservative Party MP was highly critical of both the UK’s approach to negotiating the deal and the details of what was eventually agreed.

“The truth of the matter is that the UK gave away far too much for far too little in return,” he said.

Eustice, who led the Department of Environment, Food and Rural Affairs (Defra) until September 2022, acknowledged there were “deep arguments and differences” within the UK government about the Australian deal.

The trade agreement, signed in December 2021, will eventually give Australia full tariff-free access to the UK market for beef, sheepmeat and dairy.

“Since I now enjoy the freedom of the back benches, I no longer have to put such a positive gloss on what was agreed,” Eustice said.

The former agriculture minister was particularly critical of former Prime Minister Liz Truss, who led the Department for International Trade during negotiations with Australia.

He said Truss insisted trade talks should be completed by June 2021, when then Australian Prime Minister Scott Morrison was due to visit the UK. “From that moment the UK was repeatedly on the back foot,” Eustice said.

He urged the UK government to take a different approach to ongoing trade talks with Canada and the Trans-Pacific trade partnership, known as CPTPP. “Unless we recognise the failures the Department for International Trade made during the Australia negotiations, we will not be able to learn the lessons for future negotiations,” Eustice said.