A council-owned energy company has disclosed it might not make a profit for another five years.
Annual accounts for Bristol Energy show a big increase in customers and turnover for 2018-19.
Set up in 2016, it was initially expected to be in profit by this year but has since needed more than £37m investment from Bristol City Council.
Mayor Marvin Rees said it would be "unwise" to sell the company.
Bristol Energy sold £76m of gas and electricity in the UK in the year to 31 March 2019, but running costs led to a £10m loss.
Liberal Democrat councillor Tim Kent said the company was "now the largest threat [along with Brexit] to Bristol City Council".
He added: "I actually fear for every service of the council."
Despite the fears and rising level of council money pumped into Bristol Energy, Mr Rees said: "To jump off this just as we've turned it around, with a new board, new challenges, a new business plan, a new chair and new staff would be quite unwise."
He added that new opportunities provided by the city council's commitment to energy projects to combat climate change would "change the role of the company".
Bristol Energy, which employs 180 people in the city, aimed to be "a force for social good" by reinvesting its profits back into the community.
Last month, the council made a payment of £2.5m to the energy firm as part of a plan to boost its investment to a total of £37.7m.
The long-term plan from 2019-2024 was signed off by the cabinet in April.
Bristol Energy was stripped of its contract to supply energy to the council in 2018 after being "marginally undercut" by British Gas, but the contract was reinstated earlier this year.
- 30 July 2019
- 6 April 2019
- 7 September 2018
- 3 August 2018
- 25 April 2018