KKR and Texas Pacific Group, two of the world’s biggest private equity firms, will drop controversial plans to build eight coal-fired power stations if their planned $44 billion (£22 billion) acquisition of TXU Corp is successful.

The Times has also learnt that Goldman Sachs Equity Partners, the private equity arm of the US investment bank, will co-invest with KKR and TPG.

Confirmation of the deal could come as early as today. An acquisition of TXU, including the assumption of its $12 billion debt pile, would be the biggest leveraged buyout in history. It comes only weeks after The Blackstone Group set a record with its acquisition of Equity Office Properties, the US real estate brokerage, for nearly $39 billion.

It also comes as a group that includes Texas Pacific has said that it is considering an £11 billion bid for J Sainsbury, the UK’s third-largest retailer, in what would be the biggest deal of its kind in Europe.

Sources close to the TXU transaction say that KKR, TPG and Goldman have been working on the deal for months. The cash offer is priced at nearly $70 per TXU share, a 17 per cent premium to Friday’s close. Other firms, including Blackstone, may be invited to join the consortium once the deal is agreed.

Blackstone and TPG have worked together previously in the sector. In 2004 they invested with Hellman & Friedman in Texas Genco, which is based in the same US state as TXU. They sold the stake about a year later for $8.3 billion, including debt, to NRG Energy, earning a sixfold return on the investment. The offer to scrap plans to build eight of 11 coal-fired plants comes as part of a ten-point plan designed to appease US environmental groups and persuade them to back the record-breaking buyout of the US power company.

TXU and its chief executive, John Wilder, have been embroiled in a battle with environmentalists over the use of coal-fired stations since the utility announced a $10 billion building programme last year.

Under Mr Wilder the company said it was imperative that the plants were built to meet the future demand for electricity. Critics, however, argued that increased carbon-dioxide emissions represented too high a price. “TXU was the poster child for why we need federal legislation on global warming,” said Jim Marston, the regional head of Environmental Defence in Texas, which struck the ten-point agreement with KKR and Texas Pacific in conjunction with the Natural Resources Defence Council.

“Texas Pacific called us two weeks ago, told us of its intentions towards TXU and said it wanted to make a deal with us,” Mr Marston said. “For a private equity group to call upon an environmental group like that shows just how seriously they are starting to consider the sensitive regulatory and environmental concerns around their deals.”

One source close to the talks said that TPG and KKR had to proceed with three of TXU’s coal plants because they were already under construction. The pair have pledged to cut emissions of regulated pollutants, such as nitrogen oxides and sulphur dioxide, by 20 per cent on the three proposed plants.

They also agreed to back federal legislation to impose a cap on carbon-dioxide emissions and cut TXU’s own emissions to 1990 levels by 2020.

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