Ovo workers are said to be “devastated” by the news that 1,700 jobs are to be cut by the energy firm.
Tauff was given details of the plans on Thursday, which include reducing the number of offices from 10 to three.
The unions said they would oppose job cuts, and criticized the government for “doing nothing” to tackle the energy crisis.
The cuts represent a quarter of the workforce at Ovo, which has about 4.5 million customers.
Ovo said it was raising its minimum wage by 15% to £12 an hour, increasing the wages of 1,000 employees.
The company said it would reverse the policy of offshoring from the previous owner and create more high-skilled jobs in the UK, and open a new Ovo Academy in Glasgow.
About 1,000 call center employees will be trained to become zero-carbon living consultants, with expert knowledge on everything from tariffs to green home products and technologies to make homes more energy efficient.
The remaining three offices will be in Bristol, Glasgow and London, while more employees will be supported to flexibly work from home as they wish.
The company had to apologize earlier this week after an email sent to customers advising them to keep their heating bills down by “cuddling with their pets” or eating bowls of oatmeal.
Unite Union said it warned in 2020 that Ovo was taking a risk when it took over the retail base of energy giant SSE.
Secretary-General Sharon Graham said: “We will do everything in our power to protect the jobs of our members.
“All and every option will be on the table. As a first step, the company will now have to open the books to the experts of the union.
“We will not sit and watch our members pay the price of the pandemic.”
Simon Copp, the united national official for energy, said: “We had warned the directors about a mistake in the SSE acquisition.
“In recent years those same directors have robbed accounts for an estimated amount touching 5 million pounds.
“Ovos should be subject to serious scrutiny before the union can decide on our next steps, but they will be strongly opposed by the union if they go to mandatory redundancies.”
GMB National Officer Gary Carter said: “This is a new year for employees who have seen the company through COVID and faced increased call volume and stress due to the energy crisis.
“At a time when more than 20 energy companies have gone to the wall and customers are looking to other providers for their energy needs, this is the wrong time to cut jobs.
“There is an increasing number of customers left in the energy retail sector.
“The government has backed down and has done nothing to address the energy crisis and we are all paying the price.”
Unison’s head of energy, Matt Lay, said: “The hard-working employees at the company will be devastated as they anxiously await their fate. Office closures will also take a toll on local economies.
“Employees have been dealt a brutal blow. Instead of worrying about star jumps, porridge, and cat grooming, Ovo owners should have spent time on important issues. Eliminating multiple public-facing roles puts a lot of pressure on customers. will have more impact.
“Unions will prompt managers to hold on to employees and retrain them. Those in risky roles should be part of the huge energy-efficiency drive that is required to meet net-zero commitments.
“The government is not without blame. Its pragmatic approach to energy regulation has been disastrous. Ministers need to roll up their sleeves and get involved before the entire energy sector of the UK can take over.”
Sue Ferns of Prospect Union said: “These job losses are another consequence of the crisis in the energy retail sector. The government needs to urgently focus on the wholesale reform of the energy retail market, including bringing it under the control of the local public. Consumers and employees. Paying the price for a system that doesn’t work.
“We hope that Ovo is able to live up to its promise to limit damages to voluntary redundancies. Prospect will work with the company to minimize the impact of this decision on our members as much as possible.”