Hertfordshire Police assistant chief constable Owen Weatherill said officers were “working to facilitate the rights of both the protesters and those affected by their presence” but protesters were not co-operating.
“The rights to protest are well established in this country and we remain committed to facilitating peaceful protest and ensuring compliance,” he said in a statement.
“However, at this time, the group are not engaging with us and the protest is causing major disruption to local businesses.
“At this time, 13 people have been arrested in connection with the incident, and we anticipate more arrests will be made.
“I’d like to reassure you that we are doing all we can to bring the incident to a peaceful conclusion, ensuring minimum disruption to the affected businesses.”
Merseyside Police tweeted on Saturday morning that officers were still in attendance at the Knowsley plant.
A spokesman for Newsprinters said in a statement: “This attack on all of the free press impacted many workers going about their jobs. Overnight print workers, delivery drivers, wholesale workers and retail newsagents have faced delays and financial penalty. This is a matter for the police and the Home Office.
“Thanks to other industry partners, printing was transferred to other sites.
“We apologise sincerely to any readers of The Sun, The Times, the Daily Mail, the Daily Telegraph and the Financial Times who may be unable to buy their usual newspaper this morning due to late deliveries.”
XR protesters also held a smaller demonstration near Motherwell aimed at disrupting the distribution of Saturday’s Scottish Sun newspaper.
Meanwhile, climate change protesters have been warned they risk a large fine if they fail to comply with coronavirus rules banning gatherings of more than 30 people.
The Met Police said risk assessments explaining how XR activists were minimising the possibility of Covid-19 transmission at a planned march in Westminster “did not meet the required standard”.
The force said XR’s latest round of demonstrations “pose a risk, not only to those involved, but to the wider public and communities of London”.
On Saturday a procession of activists that set of from Brighton on foot a week ago is due to march the final stretch to Parliament, depsite the fact they have been banned from taking a 20ft model boat named after teenage activist Greta Thunberg to the streets of Westminster.
On Friday Met Police assistant commissioner Louisa Rolfe warned the group not to take The Lightship Greta into an area stretching from Green Park to Lambeth.