Senedd members criticised the UK employment rights bill for “undermining” devolution and the Welsh Parliament's role, warning of “dangerous” constitutional implications for Wales.

Luke Fletcher backed the principles of the bill: “Day-one rights for workers, zero-hours contracts being revised, removing restrictions on unions [and] ending fire and rehire.”

But the Plaid Cymru politician expressed serious concerns about powers in the bill for UK ministers to override decisions made by the Welsh Government.

He told the Senedd: “We are seeing provisions that encroach on the ability of this [Welsh] Government and this place to legislate on behalf of the people of Wales.”

Mr Fletcher said: “In the same way the Welsh Government would've opposed such a power grab in the days of a Tory government, I would hope they would do exactly the same now.”

His colleague Mabon ap Gwynfor expressed grave concerns as Senedd members debated a legislative consent motion (LCM), the mechanism used to signify consent for UK bills.

He warned: “The way that this [Welsh] Government has actually introduced this, and the way that the Westminster government has approached it, is dangerous. It undermines the Welsh Government – it undermines this parliament – and it undermines devolution.”

Mr ap Gwynfor criticised so-called Henry VIII powers for UK ministers to change or overturn a law passed by the Welsh Parliament. “To me, that is entirely unacceptable,” he said.

Under the bill, Welsh ministers would need to obtain the consent of the UK Government before using powers to create a fair pay body for social care.

“We can’t continue to legislate in this way,” Mr ap Gwynfor said. “With powers being taken away from our parliament and our democratic voice being undermined time and time again.”

Warning of no Welsh scrutiny of the bill, he added that Welsh ministers opposed the use of Henry VIII powers but failed to convince their Labour colleagues in Westminster.

Mike Hedges said the Senedd’s legislation committee felt it was unsatisfactory that regulations could be used to create a devolved body under the bill.

The Labour committee chair said the Welsh Government was not content, "exhausting all reasonable avenues to challenge it” but not pursuing an amendment in the House of Lords.

Peter Fox, who chairs the health committee, expressed similar concerns, saying: “The Welsh Government has a long-standing commitment to promote fair pay in the social care workforce, yet has not brought forward its own bill.

“The effect of this choice is to severely limit the opportunities for stakeholders in Wales to be involved in the legislative process and for the Senedd to examine the policy in detail.”

Warning of a £5bn cost to businesses, his Conservative colleague Altaf Hussain said his party would vote against providing consent to the employment rights bill.

He told the Senedd: “Although the intentions behind this legislation appear commendable, I am concerned about the significant burden it will impose on businesses across the UK.”

Labour’s Hannah Blythyn, a proud trade unionist, defended the bill, stressing: “Whether we like it or not, employment rights are reserved and not enforceable at a Wales-specific level.

“If workers in the social care sector in Wales are not in scope of a UK social care negotiation body, employers would only be expected to provide the statutory minimum with regards to pay, terms and conditions, potentially disadvantaging more than 85,000 workers in Wales.”

Ms Blythyn said: “To not pass this LCM does risk leaving workers in the care sector in Wales behind, many of whom are predominantly lower paid women workers.

“I think we need to see this as a way of progressing worker rights in a sector that radically needs reform, a sector that society depends upon and a workforce, at different times in life, to whom we entrust our nearest and most dearest.”

Jack Sargeant, who is minister for fair work in the Welsh Government, said the bill will be the single biggest upgrade to workers’ rights in a generation.

Mr Sargeant told Senedd members: “It enhances employment rights, it strengthens enforcement and it removes unnecessary restrictions on trade unions.”

He agreed with Ms Blythyn, one of his predecessors as minister: “I do note some of the concerns from some members in the contributions today but we do believe it's very much in the best interest of the social care sector and social care workers in Wales.”

He criticised Tory opposition. “That's no surprise at all,” he said. “Their party, when they were in power in Westminster, consistently tried to undermine workers' rights for 14 years.”

Senedd members voted 27-13 in favour of the LCM on July 15, with Plaid Cymru abstaining.