A former EU environment commissioner has warned against backsliding on the protection of nature and the battle against the climate crisis after the bloc decided to delay its landmark deforestation law.

Virginijus Sinkevičius, the Lithuanian MEP and a vice-president of the European parliament’s Green group, said he disagreed with the decision to amend the deforestation law in order to give companies a year of extra time to ensure their products are not implicated in the felling of trees.

Every EU law “is born through a very difficult negotiation where everyone needs to give ground a bit”, he told the Guardian. “A last-minute change does not give credibility to the EU’s decision-making.”

Sinkevičius, who was EU environment commissioner for nearly five years until July, was responsible for drafting the legislation, which will ban the sale in the EU of commodities linked to deforestation such as cocoa, coffee, soy, palm oil and rubber, as well as products, including chocolate, leather and furniture.

Last month, the EU agreed a one-year delay to the lawafter intensive lobbying from industry and forested countries around the world. Sinkevičius said problems with implementing the law could have been tackled with a grace period, rather than reopening negotiations between EU lawmakers. “That additional year was a bit of a reward to those who did not try hard enough in order to comply with the legislation,” he said.

Some of the biggest companies, he said, were waiting for the law to apply, because it brings “fair competition”. He said businesses that were trying to avoid deforestation faced additional costs, against competitors that would “cut corners” on nature protection and yet “be on the same shelf in the shop”.

In 2023, 6.37m hectares of forests worldwide were lost to cattle raising, crop growing, mining, road building or devastating fires among other causes, according to the Forest Declaration Assessment.

Sinkevičius was speaking at the start of a new five-year term for the EU institutions, with growing pressure to roll back elements of the green agenda. MEPs in the European parliament, which has a record number of far-right lawmakers, have proposed cancelling the 2035 ban on selling petrol and diesel cars, as well as suspending pollution trading (a CO₂ reduction strategy) for heavy industry.

Speaking in general about green policies, Sinkevičius said “it would be the biggest possible mistake to now shift to reverse gear”, adding that the “clean industrial deal” promised by the new commission in its first 100 days would be “an important first test of how we see our economy of the future”.

Ursula von der Leyen, the European Commission president, has pledged a “clean industrial deal” for “competitive industries and quality jobs” although details remain sparse.

Sinkevičius was the EU’s youngest ever commissioner when he took charge of EU policy on environment, fisheries and oceans in 2019, aged 28. Protecting nature was always an “uphill battle”, he said, as business sees fewer opportunities in conserving soil, forests, seas and oceans than investing in clean energy. But he expressed confidence that the new commission had not forgotten nature protection, despite the headline focus on Europe’s lagging economy.

During his time in office, von der Leyen scrapped the ambition to halve pesticide use by 2030, after angry protests by farmers. Sinkevičius said he had always been critical of that target, which he described as “overkill”. He contended the 50% reduction target was unfair on member states that had already reduced pesticide use:“When I have to cut 50% from a very little amount, that’s going to be painful … while I see that my neighbour is cutting 50% from 20 times bigger [starting point]. And that was a big issue. And therefore I was suggesting that we need to find more tailor-made solutions.”

The draft pesticides law, in fact, accounted for differences in historic use of pesticides by setting national targets, requiring different efforts, underneath the headline 50% reduction goal for the EU. Asked for clarification, an aide to the MEP said he stood by his earlier remarks.

As a former European commissioner, who was required to put aside his party affiliation, Sinkevičius said he hoped to be a bridge between the Greens and other mainstream pro-EU groups in the European parliament, the centre-right European People’s party, the Socialists and the centrist Renew group.

He acknowledged the Greens could be isolated if the centre-right chose to look further right for allies, but said: “If you want a truly pro-European coalition, the Greens is your answer because we are stable, we are reliable.”