A high-profile barrister backed plans to make it a criminal offence for Senedd members and candidates to deliberately deceive the public.

Sam Fowles, of Cornerstone Barristers, gave evidence on former Plaid Cymru leader Adam Price’s proposals to disqualify politicians from the Senedd for deliberate lying.

The lawyer was involved in the Miller case against the then-Prime Minister over the propagation of the UK parliament and appeals that exposed the Horizon Post Office scandal.

Mick Antoniw, the Welsh Government’s counsel general or chief legal adviser, last week raised concerns the deception proposals are “unworkable”.

But Dr Fowles told members of the Senedd’s standards committee: “I would be very, very confident if I was asked to defend this in a judicial review.”

He described the proposals, which are set out in clause 64 of the elections and elected bodies bill, as clearly drafted and drawing on long-established legal principles.

Vikki Howells, who chairs the committee, raised concerns about the practical ramifications of criminalisation, suggesting it may be best left to the “robust” standards process.

Dr Fowles said deliberate deception fundamentally undermines confidence in democracy, pointing out that ministers and candidates sit outside of the Senedd’s regime.

Stressing the importance of independence, the barrister warned: “As is recognised in law, the appearance of a lack of objectivity is as damaging as a lack of objectivity itself.”

He said the matter is best decided by the courts, rather than by politicians appearing to sit in judgement on themselves, because it is more likely to give the public confidence.

Jennifer Nadel, co-director of Compassion in Politics, a cross-party think tank, warned faith in democracy and the political class is at an all-time low.

“This has overwhelming public support,” she said, highlighting an Opinium poll which found 72 per cent in favour of similar measures on deception with only seven per cent opposed.

Mark Drakeford questioned the effectiveness of clause 64 in dealing with hard-to-distinguish cases “where fact and opinion collide”.

The former first minister suggested deliberate deception should be dealt with under a recall process which would allow the public to remove Senedd members between elections.

Dr Fowles said clause 64 would help ensure politicians tell the truth, concluding: “It’s only by giving the public that guarantee that we can start to restore trust in politics.”

A crunch vote will be held during a three-hour debate about the proposals in the Senedd on 2 July.