The UK automotive industry is privately lobbying against the proposed 2040 introduction of a ban on sales of new diesel trucks, amid a split between manufacturers over when heavy goods vehicles should abandon fossil fuels.

In July the government revealed plans to ban internal combustion engines in new lorries after 2040, following a ban on petrol and diesel cars after 2035 to help tackle the climate crisis. It is now consulting on the measure.

The automotive lobby group, the Society for Motor Manufacturers and Traders (SMMT), says publicly that the proposed ban is a “bold commitment” that would require financial support from the government. However, it has told MPs privately that a ban should be delayed, according to responses to the official consultation.

The responses were obtained through a formal request by InfluenceMap, a thinktank that tracks climate lobbying, which shared them with the Guardian.

The Road Haulage Association (RHA), which represents trucking companies, said the ban should be delayed until 2045 for lorries over 32 tonnes in weight. It supported earlier bans for smaller lorries.

Some individual truckmakers do support bans on internal combustion engines in heavy goods vehicles in 2040 or earlier, the responses show. They include Volvo Trucks and Renault, both owned by Volvo Group, the world’s second biggest truckmaker, as well as DAF Trucks and Tesla.

Car sales are already moving rapidly to electric power, but heavy goods vehicles are much harder to electrify because of the heavy loads they carry over long distances, making batteries much less effective. Lorries were responsible for 19m tonnes of CO2 equivalent in 2019, 16% of UK emissions from transport, according to government figures.

Ben Youriev, a transport analyst at InfluenceMap, said: “Cutting emissions from road transport will be critically important for the UK achieving its net zero targets, yet the UK’s automotive industry group is lobbying to make that task harder. The SMMT is siding with its most regressive members to oppose a 2040 UK phase-out date for heavy-duty vehicles, despite the recommendations of the UK’s Climate Change Committee.”

The SMMT consultation response said: “Without clarity on the viable future solutions required for zero-emission HGVs, we do not support setting an end-of-sale date.”

It said the industry was committed to zero-emission HGVs “where technology options are viable and the business case for investment allows”, but that “some specific use cases are likely to be more challenging”.

Mike Hawes, the SMMT’s chief executive, said in a statement: “SMMT and its members do not oppose setting an end-of-sale date, but we need plans before bans. The HGV sector is committed to be fossil fuel free by 2040 and in some use cases it will be possible to switch to zero-emission trucks before this date – but at present there is no clear alternative technology available for every single HGV operation.”

Rod McKenzie, the managing director of policy at the RHA, said more time was needed for the largest lorries only because the technology to power them was not yet available. He said that would mean small delivery companies were faced with financial risks when buying new vehicles.

“It’s not that we’re against cleaner air or phasing out diesel lorries,” he said. “The question has always been the timescale.”

Tesla, the world’s most valuable automotive company, was a notable advocate in its response for the earliest ban possible, arguing for 2035. Controlled by Elon Musk, whose stake has made him the richest man in history, Tesla is aiming to produce the Semi, a heavy goods vehicle powered by batteries. However, the Semi is still “in development” despite Musk in 2017 saying it would start production in 2019.