Thousands of British Gas workers could stage a Christmas walkout in a row over new contracts.
The GMB union warned that industrial action could be held over the festive season if there is a yes vote, although it has pledged to exempt the elderly and vulnerable in homes without heating.
GMB national officer Justin Bowden said: “British Gas issued an ultimatum in July to fire and rehire 20,000 workers in the middle of a national health emergency.
“GMB warned them that members were angry, with a 95 per cent vote for action in August. We sought to get the threat off the table. The best that they were prepared to do was postpone the ultimatum until January.
“This is an insulting response to these essential workers – keeping homes across the nation heated in the depths of winter. Anger has boiled over as members have now seen the full proposals and how they impact them.
“GMB has responded by giving the go-ahead for an official national strike ballot. We will shortly announce the dates for the ballot.”