Council contractor Amey say a 'masked' Sheffield tree protester was restrained because he was 'carrying scissors in a bag'.
Amey said it has been left with 'no choice' but to bring in security guards to stop protesters encroaching on cordons put up by workers.
Following a series of stand-offs between both sides at tree felling sites, a High Court judge granted Sheffield Council an injunction which prevents people from entering, or encouraging others to enter, safety zones erected around trees.
Photographs and videos emerged on Monday of hired security staff confronting tree felling objectors who breached the injunction.
But an Amey spokesman said the man was confronted after he was carrying 'a pair of scissors, which were seen protruding from a plastic bag' and was 'restrained due to personal security concerns for himself and onsite workers'.
And a call has been made to suspend Sheffield's controversial tree-felling programme until an investigation has been held into the incident.
Laura Gordon, who intends to stands for the Liberal Democrats at the next general election in Sheffield Hallam, called for an immediate suspension in felling while an investigation takes place into 'who made the decision to use force' on tree campaigners.
She said: “Throughout the tree saga, we’ve seen an escalation in behaviour. They started with waking residents up at 5am, then they moved onto arresting campaigners and using private detectives. Now we’ve seen people wrestled to the floor. This is a pattern that is tracing a dark picture of our city.
“The council are needlessly escalating this. I don’t understand how they think it is okay to use force when dealing with peaceful campaigners. Behaviour like this is inexcusable and the council need to call it out.”
Lib Dem leader on Sheffield Council, Shaffaq Mohammed, added: “I am deeply worried about the fact that rather than opening a dialogue with tree campaigners, the council decide to wrestle them to the floor. Who made the decision that behaviour like this is okay?
“Trust in the council’s tree policy has now hit an all time low after felling has escalated to violence. I think we need an investigation into who made the decision to allow this to happen and felling needs to be suspended while this happens.
“We cannot have a council who thinks it is okay to act like this. Sheffield deserves better.”
STAG claims that cordons around trees have started to be erected by Amey workers in the middle of the night to prevent protesters from getting close to trees under threat before contractors arrive.
South Yorkshire Police said the force received 'a number of third party reports' of disputes in Lismore Road, Abbeydale Park Rise and Crescent Road yesterday.
A spokeswoman said: "Officers attended in order to keep the peace."
An Amey spokeswoman said: "We welcome peaceful protest and ask people to respect our staff, the local residents and the injunction.
"Unfortunately, some protesters are continuing to enter our legally-defined safety zones around trees, potentially putting their own, and our safety at risk.
"Continued disruption has left us with no option but to ask a professional stewarding company to help us keep people safe and within the law by preventing them from entering safety zones. This follows numerous attempts to explain to protesters that contravening Sheffield City Council’s injunction is an offence. It is a reluctant step, but one we feel we have no choice taking and for which we have the council’s support."
A Sheffield Council spokesman said: "Despite having High Court backing, city-wide support for the Streets Ahead programme, including a 600-strong increase in the number of street trees, Amey workers are being met with increasing intimidation from a small group of people who are disrupting the programme."
Peaceful protest can continue, but attempts to stop the work will be resisted, so that residents in areas where work is still to be completed will get the improvements to their roads, paths and lights that they deserve, including the replacement of trees which are damaging their streets and properties."