The EU is facing calls to ban outsourcing in the meat industry, after a Guardian investigation revealed how agency workers were exploited by companies that took no responsibility for pay and conditions.

Katrin Langensiepen, vice-chair of the European parliament’s employment and social affairs committee, said the EU should ban subcontracting across all economic sectors to ensure workers receive the same pay and conditions for the same work.

“If you have an employee working for you, you have to pay for him or her. Full stop,” said Langensiepen, a German Green elected to the parliament in 2019.

Asked whether the EU should ban subcontracting, she said: “We need EU-level social standards. We, as Greens, are crystal clear: we need minimum wage, minimum income.”

The Guardian investigation revealed how meat companies may avoid legal liability for pay, working time, accidents and injuries by hiring workers through a variety of intermediaries, including subcontractors, agents and agencies.

Tomas Zdechovsky, a centre-right Czech MEP and another vice-chair of the employment committee, said he would not go as far as banning subcontracting, but said companies must guarantee all workers were subject to the same rules.

“While we must give companies the option to use subcontracted workers to answer specific needs arising in specific times, such as during the pandemic, the EU must also guarantee that subcontractors follow the same set of rules applicable to the rest of workers in the companies that use their services,” he said.

The problems in the meat industry were also evident in other labour-intensive industries, such as construction and food delivery, said Claes-Mikael Stahl, deputy secretary general of the European Trade Union Confederation (ETUC). “There is a long chain of subcontracting, which … are structures for enabling low-wage competition to take in migrants at low cost and in precarious conditions,” he said of such industries.

Ines Wagner, a professor at the Norwegian Institute for Social Research, said she had found “the same conditions and grievances” aired by meat-industry workers during her research in 2015. “That’s quite disconcerting,” Wagner said.

Since then, some countries have tightened up the rules. After an outbreak of coronavirus in large meat-processing plants in Germany, the government there banned subcontracting in the industry with fines of EUR30,000 (GBP25,000) for rule-breaking companies. However, the ban on subcontracting contained loopholes, such as exemptions for small firms and during the summer barbecue season for the first three years the law is in force.

The EU has also created the European Labour Authority, which is charged with upholding EU law on working standards and the movement of labour. Jean-Claude Juncker, who proposed it as the the-then European Commission president, said in 2017: “In a union of equals, there can be no second-class workers. Workers should earn the same pay for the same work in the same place.”

The ELA began work in 2019, but will not be fully operational until 2024.

In 2018, the EU agreed to overhaul the rules on “posted workers” – EU nationals sent by their employer to work in another member state. Posted workers pay national insurance contributions to their home country, rather than to the country where they work. This allows posted workers from central and eastern Europe countries to offer cheaper services in western Europe, where labour costs are higher.

Posted workers number only about 2 million people – under 1% of the labour force, compared with 17 million “mobile workers”, or EU nationals who use their right to live or work in other member states.

The changes were a victory for the French president, Emmanuel Macron, who was elected on a promise of a “Europe that protects” and wants to reduce differences in pay and conditions. Under the new rules, posted workers can only work for lower salaries for one year, after which they must be paid the same as the domestic workforce.

But Stahl, the trade unionist, sees problems with EU rules on posted workers. He recalls a case in his native Sweden, where one Polish company won 59 contracts to refurbish houses over 11 years while continually claiming they were hiring “temporary” posted workers. “That’s just one example of how companies use the internal market to compete on low wages,” he said.

In emailed comments to the Guardian, the EU commissioner for jobs and social rights, Nicolas Schmit, said: “I find reports of poor working conditions, non-transparent terms or inhumane treatment of workers completely intolerable.

“Some countries have already taken action and clamped down on poor working conditions in slaughterhouses, but more progress is needed. I urge all member states to redouble their efforts to ensure that EU labour laws are properly enforced by all companies and in all sectors, as well as to follow up with inspections as needed.”

Trade unions fear that national governments are struggling to uphold and enforce labour standards, after wide-ranging cuts since the financial crisis.

Research by the ETUC found that workplace safety inspections in the EU had fallen by a fifth since 2010, while there had also been a loss of 1,000 safety inspectors – 7% of the total. The cuts were deepest in Portugal and Malta, which each saw a 55% reduction in inspections. Even the bloc’s biggest economy, Germany, saw a 25% fall in inspections during this period.

The ETUC has yet to be convinced by the fledgling European Labour Authority, accusing it of failing to take action over dozens of cases of labour exploitation last year, including unpaid and underpaid wages of EU and non-EU migrant workers.

Attitudes to labour market regulation were undergoing a generational change, Stahl said. “For almost 20 years the EU has been used as a structure to enable wage competition and that [view] has just shifted.” Recent legal changes showed the predominant view now was “that the EU should be used as an instrument to prevent wage competition,” he said. “That’s an important shift but, of course, we are not there yet.”

Wagner said current labour market structures were reinforced by social factors – workers in relatively poorer eastern European and non-EU countries seeking higher wages, as well as employment contracts that create dependency, such as travel to the destination country, accommodation and transport to the workplace often being paid for workers in farming and food processing.

“As long as this dependent relationship is within reasonable acceptable grounds for the workers, then it might continue,” she said. Workers will only get out of exploitative jobs, “when there is no [more] work, or there is no salary paid at all”.

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