Plans to ensure equal representation of women in the Senedd have been described as a waste of time, energy and resources due to the likelihood of legal roadblocks.

Darren Millar criticised Welsh ministers for bringing forward the Senedd Cymru (Electoral Candidate Lists) bill despite concerns that it is not within the Welsh Parliament’s powers.

The Conservatives’ shadow constitution minister said plans for legally binding gender quotas in future Senedd elections would impact equalities law which is reserved to Westminster.

He told the chamber: “It is extraordinary that this Senedd is spending time, energy and resources focusing on a piece of legislation that it does not have the competence to be able to deliver, rather than focusing on the everyday concerns of the people of Wales.”

Mr Millar raised alarm about the potential costs, warning: “There’ll be significant legal challenges if this bill goes forward, not least, probably, in the Supreme Court.”

Elin Jones, the Senedd’s speaker or Llywydd, wrote to all MSs this week, setting out her view that the bill would not be within the Welsh Parliament’s powers.

Following legal advice, she wrote: “I considered the purpose and effect of the bill.

“While I accept the bill has the devolved purpose of making the Senedd a more effective legislature, in my view the bill also has the reserved purpose of equal opportunities.”

Ms Jones said the question of whether the bill is within the Senedd’s powers can only be definitively answered by the Supreme Court.

Her statement on legislative competence does not affect whether the bill can proceed, but it could later be referred to the Supreme Court by the UK Government’s attorney general.

Mr Millar raised concerns about the bill’s legislative process being cut short in the Senedd, with less time than usual for committee scrutiny and amendments.

He warned: “You're going to chop down the opportunity for the committee to undertake its important work, in spite of the huge question marks over the competency of this Senedd.”

Challenged by the first minister about a lack of diversity on the Conservative benches, Mr Millar recognised political parties need to do more to address under-representation.

However, he argued people should be elected on the basis of merit.

He criticised a lack of a mandatory “zipping” process for candidate lists, saying: “The bill provides for lists to be entirely made up of women but not men. There's no equality there.”

Describing the plans as groundbreaking, Jane Hutt, the member in charge of the bill, outlined the Welsh Government’s position in a statement to the Senedd on March 12.

Wales’ equality minister told the chamber: “The purpose of the bill is to establish a more effective Senedd, and, as such, the bill is within the Senedd's competence.

“And I think that point about purpose is crucial to this.”

Ms Hutt quoted the Government of Wales Act 2006 as saying the question of whether a bill relates to a matter reserved to Westminster is determined by reference to its purpose.

“That's the test about competence,” she said. “The purpose of this bill is to establish a more effective Senedd. Surely we can unite on that goal, to deliver a more effective Senedd?”

Ms Hutt added that a tight timetable is required to ensure the reforms are in place before the next Senedd election in 2026.

Heledd Fychan, for Plaid Cymru, said the bill would make the Senedd more representative of the people that it aims to represent and make the institution more effective.

She pointed out that less than a third of the 470 candidates put forward by political parties were women in the 2021 Senedd election.

Ms Fychan said: “Gender quotas for elections are commonplace around the world and are now used in more than 130 countries.

“Evidence from countries such as Spain, Belgium and Ireland shows that gender quotas can be an effective means of increasing the number of women elected to parliaments.

“The number of women in the parliaments of 11 EU countries that used gender quotas increased almost three times faster than in EU countries without quotas.”

Adam Price, the former Plaid Cymru leader, said: “Having fair and equal representation for all is a victory for all. That is the essence of what you are seeking to achieve with this bill.”

Mr Price said the bill would be a fundamental step forward and the same mechanism could be used in future to address the whole range of diversity.

Vikki Howells, a Labour MS who represents Cynon Valley, raised the example of Ireland, which introduced gender quotas in 2016.

Ms Howells said Ireland has since seen a 90% increase in the number of women candidates and a 44% rise in the number of women elected.

Huw Irranca-Davies, a fellow Labour backbencher, who chairs the legislation committee, suggested the issue of whether the bill is within Senedd powers is likely to be contested.

The Ogmore MS backed the policy’s intended aim, saying: “The progressive road is not always the easy road, but it is the right road.”