Volunteers have been labelled a "scab army" for helping clear waste during a long-running bin strike, which a union now warns could last until Christmas.
The Bearded Broz, who have cleared 45 tonnes of waste in Birmingham during the six-week strike, were criticised in the socialist Morning Star.
The group said it respected workers, but wanted to clean the streets.
The Unite union warned on Friday action could continue "unless the city council negotiates a fair settlement".
Labour-run Birmingham City Council said it was "very disappointed" by the union's warning and said Unite was "effectively holding the city to ransom".
The article published in the Morning Star said: "The community group, known as Bearded Broz, are encouraging people to join their scab operation as they undermine the strike by Birmingham City Council refuse workers over job losses."
However, Naveed Sadiq from the group, which was set up and run by volunteers from the Muslim community, said members had met refuse workers, who said they "respected" the team for taking care of their areas.
Mr Sadiq said the respect was mutual: "We can see the work that they do and respect them for the work that they do.
"We don't undermine them at all, we don't have a personal agenda or a personal grief with the binmen. Our issue is, these are our streets and we're gonna do something about it.
"If you want to call me a scab, that's fine."
The BBC has asked Unite to respond to the comments made about the Bearded Broz, but the union is yet to comment.
The council had said earlier positive discussions were continuing with unions and it had visited more than three-quarters of the city's 8,200 streets as part of its "operation to ensure all wards receive refuse collections during the industrial dispute".
However, on Friday Unite said it was balloting refuse collection members to renew its industrial action mandate, which could result in more strikes after the present round ends on 21 September.
Unite assistant general secretary Howard Beckett said: "We continue to hold talks with the council, but progress has been slow and we would call on the council to now step up and conclude this urgently."
The union will ballot members on 17 August. The ballot closes on 31 August.
Councillor Lisa Trickett, cabinet member for clean streets, recycling and environment at the city council, said: "We are very disappointed by this latest development.
"Unite are effectively holding the city to ransom with this announcement.
"They have talked about red lines they wish to negotiate with us, but this threat of extended industrial action will not help the process of achieving a swift resolution so we can get on with delivering a modern, effective and efficient refuse collection service for the people of Birmingham.
"We have put the offer of [conciliation service] Acas to Unite as an open, fair and transparent way of ending the dispute."
Meanwhile, action escalated on Friday, with the three-hour stoppages being split into three separate hour-long blocks, spaced out across the shift.
It means workers will return to their depot - which they also do for breaks - three times a day.
Previously they had taken a two-hour stoppage from 06:00-08:00 and a one-hour stoppage between 12:30-13:30.
The BBC has contacted the Morning Star for comment.