Boris Johnson warns Sunak he ‘cannot afford to falter’ on net zero commitments

Boris Johnson has waded into the row over Rishi Sunak’s plans to U-turn on some of the government’s net zero commitments, warning his successor that he “cannot afford to falter now” or “lose our ambition” for the country.

The former prime minister, who oversaw the introduction of many of the targets during his tenure, said “businesses must have certainty” about the UK’s net zero commitments, as companies reacted with alarm to the potential policy shift.

Related: ‘Pathetic’: what scientists and green groups think of UK’s net zero U-turn

The business backlash to Sunak’s plans, which are an attempt to create a dividing line with Labour before the next election, forced Sunak to bring forward a speech to Wednesday to fend off criticism that the move would deter firms from investing in Britain.

Johnson, who is no longer an MP, is the most senior Conservative yet to condemn the decision to water down the targets, a move that it is argued could cost jobs, put up energy bills and damage the UK’s international reputation.

Sunak held a hastily arranged call with cabinet ministers on Wednesday morning after speculation about his net zero plans emerged on Tuesday night.

In a statement, Johnson said: “Business must have certainty about our net zero commitments. This country leads on tackling climate change and in creating new green technology. The green industrial revolution is already generating huge numbers of high-quality jobs and helping to drive growth and level up our country. Business and industry – such as motor manufacturing – are rightly making vast investments in these new technologies.

“It is those investments that will produce a low-carbon future – at lower costs for British families. It is crucial that we give those businesses confidence that government is still committed to net zero and can see the way ahead. We cannot afford to falter now or in any way lose our ambition for this country.”

After his climate proposals leaked on Tuesday, Sunak said the government remained committed to the net zero target but planned to hit it in a “better, more proportionate” way.

In an apparent dig at Johnson, he said politicians of “all the stripes” had not been honest about “costs and trade-offs”, and he accused previous governments of taking “the easy way out, saying we can have it all”.

The Guardian understands that the move will include delaying a ban on the sale of new petrol and diesel cars, currently due in 2030, watering down the phasing out of gas boilers and dropping plans for new energy efficiency targets for private rented homes.

However, Sunak has recommitted to the target of net zero emissions by 2050, insisting his government was not “losing our ambition or abandoning our commitments” on the climate crisis.

The potential policy shift also alarmed the car industry, which has invested on the basis of a 2030 shift away from petrol and diesel. Ford UK’s chairwoman, Lisa Brankin, said: “Our business needs three things from the UK government: ambition, commitment and consistency. A relaxation of 2030 would undermine all three.”

Chris Norbury, the chief executive of the E.ON energy firm in the UK, said the move would be a “misstep on many levels” as he hit out at the “false argument” that green policies could only come at a cost, arguing they delivered affordable energy while boosting jobs.

“In our homes and communities we risk condemning people to many more years of living in cold and draughty homes that are expensive to heat, in cities clogged with dirty air from fossil fuels, missing out on the economic regeneration this ambition brings,” he said.