The motion stressed there was no ‘one-size-fits-all’ solution and that agile responses to changes in the economy and employment patterns were key.

Mover Denise McGuire, Prospect’s vice-president, said membership figures told a stark story, with a fall from 11 million 30 years ago to 6.4 million today. “In the private sector less than one in five are covered by collective bargaining and membership density is just over 14%.”

However, these levels were not spread evenly – lowest were construction, communications, manufacturing, sales and customer service, with part-time workers also losing out, “as always.”

Young people tended to have their first experience of jobs in a union-free environment. They were more internet savvy and usually expected to get information and advice for free.

One union in the Netherlands had given up trying to recruit those under 30, instead providing a website and Q&As on the world of work paid for by advertising revenue and sponsored by MTV – “No collective spirit, no common values – not even a union logo.”

Private sector workers were more likely to seek help from Citizen’s Advice, friends, colleagues, solicitors or the internet before approaching a union.

“We’ve got to change that. A strong union membership in the public sector needs a strong membership in the private sector.”

In her sector, communications, members were facing union-busting attempts, outsourcing and offshoring. Colleagues coerced into signing personal contracts had been relieved when Prospect won back collective bargaining for them.

“Let’s go for growth – more people, more young people, more people active in their unions,” McGuire concluded.

Lindsey Adams (Unite) said her sector, finance, had a long history of union organisation. But in many parts of the private sector job insecurity, casual labour and high attrition levels were all obstacles. People often had individual, secret pay arrangements and there was no equality duty, widening the pay gap between men and women.

USDAW’s Paddy Lillis said it was vital to make unions more relevant to those facing tough times, job insecurity, pay uncertainty and fears for the future. USDAW had shown it was possible to organise within the private sector, with over 60% union density in many parts of retail.

For Community, John Edgar said that as well as finding innovative ways to reach potential members, it was necessary to educate employers.

Delegates from the Society of Radiographers, Unison and GMB also spoke in favour.