Opposition parties in Wales have criticised the Labour-led government for blocking the publication of a report examining claims that the sacking of Carl Sargeant from his ministerial post was leaked in the days before he killed himself.

The Welsh Tories claimed during a assembly debate that it was morally wrong for the report not to be published.

It was one of three reports commissioned after Sargeant was found dead, having been dismissed as communities secretary following allegations about his conduct towards women.

The report found “no evidence of prior unauthorised sharing of information” about his sacking, according to a short statement issued after its conclusion.

Opposition parties have said it should be published in a redacted form, but Welsh ministers claim this could still identify witnesses. The first minister, Carwyn Jones, tried to halt the debate by claiming it was unlawful and saying he could take legal action.

During the debate on Wednesday the leader of the Welsh Conservatives, Andrew RT Davies, said safeguards could be put in place to protect witnesses. He told Labour backbenchers that if they did not support him, “morally you will be found wanting”.

The Plaid Cymru AM Adam Price said denial of information was “always suspect” while the Ukip leader at the assembly, Neil Hamilton, branded the threat of legal action to halt the debate an “extraordinary reprise of the kind of action we saw in the 1640s” – a reference to King Charles I’s aggressive approach to political opponents in England.

The counsel general Jeremy Miles, whose job includes providing legal advice to the Welsh government, said witnesses might be reluctant to cooperate in future inquiries if the report was published.

Before the debate in a letter to the presiding officer, Elin Jones, the first minister wrote that if the Tories’ motion were not withdrawn, he reserved the right to bring proceedings for judicial review.

The presiding officer replied: “I have taken advice and carefully considered your arguments. Having done so, I am not persuaded of the case which you have advanced. As a result, the motion remains scheduled for debate.”

Meanwhile, another inquiry, into whether Jones misled the assembly over what he knew about claims of bullying in the Welsh government dating back to 2014, has concluded that he did not breach the ministerial code.

Headed by James Hamilton, a lawyer, the inquiry said answers given by the first minister in the assembly were accurate and truthful.

The third, and main inquiry, headed by Paul Bowen QC, is yet to begin and is expected to take several months.

The attempt to force the publication of the report failed. Twenty-six assembly members backed the Tory motion calling for it to be released, one abstained and 29 voted against.