"The country is in danger of creating a nebula that has the effect of never catching those responsible," the president, Marcelo Rebelo de Sousa, said during a visit to Madeira.

"One of the effects of wanting to shoot in all directions" – as he summarised the current state of the debate and "political speculation" – may be to take the focus off what is essential and "arresting those responsible may never be done".

What matters to him, he stressed, “is to arrest those responsible”, but “it sometimes seems that it is on purpose that every time we should leave scope for the investigation, so that it can go deeper, a nebula arises that has as its … effect bringing together a range of clues that obviously do not facilitate the investigation.”

The president reiterated that he himself knew nothing of any "cover-up" in the case, saying that was “something from another world" to think that he could have knowledge of it and at the same time keep publicly insisting on the need to clear up the case.

"There is no new data," he said, when questioned by journalists in Madeira, about the possibility that a senior aide of his might have been aware of an alleged cover-up of the theft from the Tancos depot and later return of the weapons.

De Sousa recalled that his former chief military aide, General João Cordeiro, had two weeks ago said that he knew "nothing at all" about the memorandum written by Major Vasco Brazão, then former spokesman for the military police force, the PJM, for the attention of the office of the minister of defence. Cordeiro had also, he added, said that “there was never on the military part of the office of the presidency any knowledge of what emerged as a cover-up and now is no longer a cover-up.”

He recalled that when he visited Tancos on 4 July last year, five days after the army made public the fact that the cache had disappeared, there was no talk of any cover-up.

In his comments in Madeira, the president went on to question why he would repeatedly insist on the case being cleared up if he in fact was aware of any cover-ups.

"If I today knew who had stolen them, I wouldn’t demand clarification,” he said. “If today I knew the fate of the weapons, I would not demand clarification.

He had been insisting on the need to clear up the case, he said, because he “doesn’t know” what happened.

The theft of military material from Tancos – including anti-tank grenades, plastic explosives and a large amount of ammunition – was announced on 29 June last year. Most of the material was later said by the PJM, in a statement on 18 October 18, 2017, to have been recovered at Chamusca, some 20 km from the where it had gone missing.

An investigation by public prosecutors and police into the re-appearance of the stolen material, called Operation Hubris, on 25 September led to the detention of several members of the military police and national guard. According to the prosecutors, the suspected crimes under investigation include criminal association, denial of justice, malfeasance, document forgery, graft, abuse of power, illegal possession of weapon, and arms trafficking.

The case led to the resignation on 12 October this year of the defence minister, José Azeredo Lopes, who said that "political attacks" on him were harming the armed forces.

The army chief of staff, General Rovisco Duarte, submitted his resignation, two days after the new minister, João Gomes Cravinho, took office.