An advocacy group urged the N.C. Utilities Commission on Monday to reopen hearings into Duke Energy’s proposed merger with Progress Energy.

The N.C. Waste Awareness and Reduction Network, an anti-nuclear group in Durham known as WARN, argues that circumstances have changed since the commission’s hearings last September. New hearings, if granted, would likely derail the utilities’ plan of closing the $26 billion merger by July 1.

WARN cites new merger conditions imposed by federal authorities, confidential settlement agreements with customer groups filed in May and rising costs of the nuclear power plants the combined utility might build.

It says that “due to the sheer size, complexity and sweeping, long-term ramifications of this arrangement, the commission must ensure a full and careful examination of all these issues, not compress its review to accommodate the utilities’ much-publicized pressure that their deal needs to be closed by any certain date.”

The utilities commission had set Monday as the deadline for formal parties to the merger proceeding to file comments. The utilities and the state’s Public Staff, which represents consumer interests, have until Tuesday to file rebuttals.

The N.C. Sustainable Energy Association, which advocates for renewable energy, and four environmental groups also asked the commission Monday to add conditions if it approves the merger.

A June 8 order from the Federal Energy Regulatory Commission approved the merger with conditions that are likely to cost Duke and Progress more money to meet. The utilities have guaranteed $650 million in savings for Carolinas customers over 6 1/2 years.

WARN said 14 confidential settlement agreements between the utilities and customer groups, cooperatives and municipalities could erode benefits to ratepayers or shift costs among customer classes.

The group also asserts that Duke and Progress will spend more heavily on nuclear plants than envisioned last year.

WARN claims South Carolina officials, in return for supporting the merger, are pushing Duke and Progress to buy into the Summer nuclear plant near Columbia. Duke is exploring buying a 5 percent to 10 percent stake in the two new reactors being added to the plant.

Last week WARN cited an anonymous source in saying extensive repairs needed at Progress’ Crystal River nuclear plant in Florida could derail the merger. Duke says it is monitoring that situation but expects to close the merger.

In a separate filing, the Southern Environmental Law Center, representing four groups, repeated a proposal that the new Duke-Progress be required to spend $50 million over five years to boost renewable-energy technologies such as offshore wind.

The N.C. Sustainable Energy Association said the commission should analyze the merger’s effects on electric rates and on diversifying energy sources with renewable energy.

The association said the commission should make Duke and Progress set up funds to help low-income customers pay for energy-efficiency measures; offer financing to customers; and set up a pilot program to let renewable-energy generators sell directly to consumers.