The GMB says there is a 'profits at all costs' culture at British Gas
Staff at British Gas have voted to strike after alleged bullying by management, and over changes to staff terms and conditions.
The GMB trade union said staff would take industrial action over what it described as "macho management".
The union said its members supported strikes by 82%, and industrial action short of a strike by 90% in a high turnout of the 8,000 workers balloted.
British Gas said it had yet to be told the reasons behind the dispute.
And Matthew Bateman, director of heating services at British Gas, said the company was "disappointed by the GMB's action".
British Gas has been given a week by the GMB to respond before the union decides on its next move.
"It is now time for them to sit up and take notice," said general secretary Paul Kenny.
"We are giving British Gas a week to give us a constructive response. We want an independent inquiry into the profit-at-all-costs culture at British Gas."
Mr Kenny said there will be a meeting with shop stewards to determine what form action should take.
For British Gas, Mr Bateman said: "We are not surprised by this ballot result, given the GMB's recent false accusations and reckless scaremongering.
"The GMB has still not told us the grounds for this dispute, even though we have asked for this information several times."
He also said the firm had "robust contingency plans in place" to make sure service to customers was unaffected.
"We remain committed to talking with the GMB and avoiding this unnecessary industrial action," he added.