LONDON — Britain’s plans to build a fleet of nuclear power plants by 2025 are “ambitious” at best and “unrealistic” at worst, according to a report to be released Monday by a committee of the House of Commons.

“It is worrying that the government does not have any contingency plans in place for the event that little or no nuclear is forthcoming,” the Energy and Climate Change Committee wrote in its report.

Replacing the country’s aging network of nuclear power stations is a major component of the government’s strategy to lower 1990 levels of greenhouse gas emissions by 80 percent by 2050. While nuclear power has disadvantages, particularly the production of radioactive waste, it emits virtually no greenhouse gases.

The French utility EDF and the British government are negotiating the terms for developing new nuclear plants. EDF has proposed constructing two plants at Hinkley Point on the Severn Estuary in southwest England, where the company operates two nuclear stations built in the 1970s. The new plants would be the first for Britain since 1995.