Staying in the European Union is in the best interests of Britain, with the referendum campaign a chance to push for more public ownership of local services, Jeremy Corbyn will say on Saturday.

The Labour leader is expected to stress that he will push for changes in Brussels beyond migration and welfare that would strengthen workers’ rights and end pressure to privatise public services.

“In the referendum campaign Labour will be making it clear we stand up for public ownership and accountability,” Corbyn will say in a speech to the Association of Labour Councillors conference.

“Our party is committed to keeping Britain in the EU because we believe it is the best framework for European trade and cooperation and is in the best interests of the British people.

“But we also want to see progressive reform in Europe: democratisation, stronger workers’ rights, sustainable growth and jobs at the heart of economic policy, and an end to the pressure to privatise and deregulate public services.”

At the address in Nottingham, Corbyn will say he wants councils to have greater freedom to spend and borrow to fund investment in local services, with similar powers to European cities to take control of water and energy provision.

“Privatisation isn’t just about who runs a service, it’s about who services are accountable to. It’s about who shares the rewards, about protecting the workforce and getting a good deal for local people who use the services,” he will say.

“We will give councils greater freedoms to roll back the tide of forced privatisation. That’s what’s been happening across Europe – where scores of cities across our continent have been taking water, energy and other services back into local public ownership.

“We want to deliver the very best for our communities and deliver the very best services: locally run, locally owned and locally accountable.”

Corbyn, once considered lukewarm to the prospect of staying in Europe, has now committed himself to campaigning for a vote to remain in the EU.

His speech in which he will promise to fight for “a real social Europe during the coming referendum campaign” comes as the Labour group calling for Brexit was in deep division over whether it was affiliated to one of the main leave campaigns.

Former Labour minister Kate Hoey and Labour donor John Mills – the leading lights of the Labour Leave group – are in conflict over ties to Vote Leave, which is one of two campaigns vying to gain the Electoral Commission’s designation as the main Brexit campaign.

Hoey has expressed concern about the role in Vote Leave of its campaign director, Dominic Cummings, a former aide to Tory cabinet minister Michael Gove, saying Labour Leave did not intend to align itself with either Vote Leave or its rival Leave.EU.

Cummings has been accused by critics in the Brexit ranks of a brusque and insensitive manner. On Friday, Arron Banks, a senior Ukip donor and the founder of rival group Leave.EU called Cummings and his colleague Matthew Elliott “two of the nastiest individuals I have ever had the misfortune to meet”.

But Mills, who is also vice-chairman of Vote Leave, said: “Labour Leave is an independent campaign but corporately it supports Vote Leave.”

Mills said he was the “founder and co-owner of Labour Leave”, but Hoey said: “John Mills is not an office holder. He was part of the people who set it up, he was chair of Vote Leave and then during the week he was demoted to being the vice-chair of Vote Leave.”

The feud among the leading groups could result in none of them being designated as the official campaign, Banks claimed on Friday. “If it is bitterly contested, and if designating is going to be controversial, the commission has a right to choose not to designate,” he said.

Britain Stronger in Europe, which has no rival campaign, seems certain to get the lead designation for Remain.

With the main Brexit campaigns in disarray, the government is said to be trying to enlist the help of elections guru Lynton Crosby to sell the Brussels reform package deal proposed by David Cameron to the British public, according to a Sky News report. The Australian public relations expert was largely credited with the strategy that won the Tories the majority in the 2015 election.

The prime minister vehemently denied claims made on Friday by European parliament president, Martin Schulz, that his reform deal was potentially reversible, saying the package would be legally binding.

Schulz hinted MEPs might want changes made before it agreed the “emergency brake” on in-work benefits which is the centrepiece of the reform package.

Cameron claimed the UK would be able to veto any attempt to unwind the agreement, which he hopes to secure at a summit in a fortnight. “If it is agreed, it will be agreed as a legally binding treaty deposited at the United Nations,” he said.

“It would only be reversible if all 28 countries, including Britain, agreed to reverse it.”