A ban on politicians lying will be brought in before the 2026 Senedd elections, the Welsh government has promised.

Counsel General Mick Antoniw vowed to legislate on Tuesday in a move that spared the government an embarrassing defeat in the Welsh Parliament.

Labour faced losing a vote as it tried to stop a Plaid Cymru attempt to pass its own version of the ban.

Mr Antoniw promised that the law would disqualify Senedd politicians and candidates found guilty of deliberate deception from being a Member of the Senedd (MS).

BBC Wales was told that ministers cut a deal with Plaid Cymru and former Labour minister Lee Waters hours before the vote was due to take place.

In the end the government won with 26 votes for, 13 against and with 13 abstentions.

Former Plaid Cymru leader Adam Price said what had been announced was “truly historic”.

Discussions had taken place with opposition parties throughout the day, with Mr Antoniw even taking the unusual step of going to a meeting of the Conservative Party group on Tuesday morning.

In May, Mr Waters helped the former Plaid leader amend a law on the operation of elections, currently being considered by the Senedd, to introduce a new offence of deception in politics.

That was despite opposition from the Welsh government.

Mr Antoniw, who the government’s chief legal adviser, criticised the lack of consultation with the police.

In a letter to MSs he warned it presented “a serious risk of political debate being stifled and effective scrutiny of the government undermined”.

On Tuesday, he tried to have Mr Price’s offences deleted from his bill, which among other items would lay the groundwork for piloting automatic voter registration, via an amendment.

But he faced losing as the entire opposition – including Plaid Cymru, the Conservatives and Welsh Liberal Democrat Jane Dodds – united to support Mr Price’s offence.

The law, had it been passed, would have given politicians and candidates 14 days to withdraw a false statement.

If they were prosecuted through the courts they would be banned from being an MS for four years.

It is not yet clear whether the proposed law would make lying a criminal offence or a civil sanction.

In the Senedd, Mr Antoniw said: “The Welsh government will bring forward legislation before 2026 for the disqualification of members and candidates found guilty of deliberate deception, though an independent judicial process.”

He said he would invite the standards committee of the Senedd “to make proposals to that effect”.

He said it was a “matter that goes to the heart of everyone”.

Mr Price called it a “landmark moment and is a recognition that existing mechanisms to ensure public trust and confidence in politics have failed”.

He said it would make Wales the first country to outlaw political lying.

In an hour-long debate, Mr Waters, MS for Llanelli, said that “no doubt, politics in this country has become darker””.

He recounted a year in his consistency where he had encountered “lying, manipulation, racist abuse, arson” and “mobs whipped up by the visiting far right descending on the homes of those who put their heads above the parapet”.

He added: “It’s been an awful, upsetting experience seeing ugliness becoming quietly normalised.

“It’s naive… to think that democratic traditions are sacred. We mustn’t allow this… norm spoiling in any form.”

Peter Fox, Welsh Conservative, told the debate: “It is so fundamental that we try to rebuild the trust that has been diminished in in our vocation, because it’s so fundamental to democracy that we are trusted and believed.

“Sadly, that’s been eroded.”

But he said he was concerned Mr Antoniw’s proposal “might not give the parliamentary time to enable things to go forward”.

Welsh Liberal Democrat leader Ms Dodds, her party’s only MS, asked “why does lying flourish in politics?”

“Because we can get away with it. Deception can run among politicians, largely because we face no real repercussions.”