Manx Gas must agree a new regulatory deal with the government by 24 April or face having regulation "imposed" on it, the policy and reform minister said.
Chris Thomas said the "hard deadline" had been set on Manx Gas, which is the Isle of Man's sole gas supplier.
Negotiations began last year after a report into the existing deal said the company's profits were too high.
Manx Gas managing director Ian Plenderleith said he hoped a new agreement was "not far away".
While striking a deal had "taken longer than anybody expected", Mr Plenderleith said his company was "involved in extensive discussions with the government".
In 2015 Manx Gas agreed to a 9.99% cap on its profits.
A review into that agreement, published in February 2019, said the company's profits needed to be reduced still further.
Campaigner Barry Murphy said he was "tired of waiting" for an "overdue" new deal between Manx Gas and the government.
"We don't want to be paying too much for our utilities," he added. "We want a fair deal and a fair agreement."
Joined by about 15 others, Mr Murphy held a protest outside Tynwald on Tuesday before walking across Douglas to the Manx Gas headquarters.
Speaking in the House of Keys at the end of January, Mr Thomas said work on the government's Climate Change Action Plan had delayed progress in reaching a new settlement.
Under the plan, which was approved by Tynwald last month, fossil fuel heating will be banned from new homes from 2025.