Government sources have played down the idea of a cabinet split over a possible windfall tax on energy companies as the business secretary, Kwasi Kwarteng, firmly quashed the idea, days after it was mooted by the chancellor. In a search for solutions to a crisis over energy prices, and the cost of living more widely, Rishi Sunak said a windfall tax, as advocated by Labour, was possible if energy companies did not properly reinvest bumper profits. Asked if he backed the chancellor’s idea, Kwarteng told Sky News: “I’ve never been a supporter of windfall taxes. I have been very clear on that publicly, I think it discourages investment and the reason why we want to have investment is because it creates jobs, it creates wealth and it also gives us energy security.” Sunak told Mumsnet on Wednesday he was also concerned that a windfall tax could put off investment in new oil and gas extraction, but added: “If we don’t see that type of investment coming forward and companies are not going to make those investments in our country and energy security, then of course that’s something I would look at and nothing is ever off the table in these things.” Asked on Sky about Sunak’s views, Kwarteng said: “He is the chancellor of the exchequer, he is responsible for tax policy. From my point of view, I want to see investment in the North Sea.” Questioned about whether he disagreed with Sunak, Kwarteng said: “My view is that, and I’ve said this publicly many times, a windfall tax will act as a disincentive to invest and we want to see investment.” Treasury and business department sources rejected the idea of a split, saying both ministers held the same view of not seeking a windfall tax, but not ruling it out if energy companies did not provide sufficient new investment. In a letter to oil and gas companies, also released to the media, Kwarteng called on them to invest in new domestic energy production as a way to help bring down bills. “In return for the UK government’s ongoing support for the sector, the prime minister, the chancellor and I want to see a very clear plan from the oil and gas industry to reinvest profits in the North Sea and, importantly, in the clean energy technologies of the future,” he wrote. Labour, which has argued that a one-off, 12-month windfall levy would contribute £1.2bn towards wider efforts to reduce energy bills, dismissed the letter as ineffective. Ed Miliband, shadow climate change secretary, said: “Kwasi Kwarteng’s letter is not worth the paper it is written on for millions of families facing the cost of living crisis. Families want action to deal with the bills crisis, not a vacuous, insulting piece of political spin.”