On 30 May 1924, he openly spoke in the Italian Parliament alleging the fascists committed fraud in the 1924 general election, and denounced the violence they used to gain votes.

[2] In 1924 his book The Fascisti Exposed: A Year of Fascist Domination was published and he made two impassioned and lengthy speeches in the Chamber of Deputies denouncing Fascism and declaring that the last election, marked by intimidation and militia violence, was "invalid".

[3] In the speech Matteotti gave on 30 May 1924 in Parliament, he strongly contested the violence, saying: "In Naples in one conference that the head of the constitutional opposition was to hold, he was prevented due to the mobilization of the armed corps, which intervened in the city", as a fraud in the 1924 elections (however won by PNF thanks to the Acerbo Law, which put in place an electoral system that guaranteed a majority to the Fascists).

In fact, according to Renzo De Felice's essay Breve Storia del Fascismo, Matteotti publicly condemned the alliance of the socialist trade unions and the fascist counterpart.

They were Amerigo Dumini, Albino Volpi, Giuseppe Viola, Amleto Poveromo and Augusto Malacria, all acting as members of Mussolini's secret political police.

In those weeks "Fascism fielded an articulated series of misdirections, obstructions of justice and red herrings, to declare the moral question closed".

This was an attempt to give strength to the "moral question" that would point to public disapproval of fascism but also to put pressure on the King to dismiss Mussolini.

On 13 September, a right-wing fascist deputy, Armando Casalini, was killed on a tramway in retaliation for Matteotti's murder by the anti-fascist Giovanni Corvi.

Admitting that the murderers were Fascists of "high station", as Hitler later did after the Night of the Long Knives, Mussolini rhetorically claimed fault, stating "I assume, I alone, the political, moral, historical responsibility for everything that has happened.

Five men (Amerigo Dumini, the operational leader of the Ceka, the Fascist secret police; Giuseppe Viola, Albino Volpi, Augusto Malacria, and Amleto Poveromo) were arrested a few days after the kidnapping.

After the Second World War, in 1947, the trial against Francesco Giunta, Cesare Rossi, Dumini, Viola, Poveromo, Malacria, Filippelli and Panzeri was re-opened.

John Gunther wrote in 1940 that "Most critics nowadays do not think that the Duce directly ordered the assassination ... but his moral responsibility is indisputable", perhaps with underlings believing they were carrying out Mussolini's desire by performing the kidnapping and murder on their own.

[11] Other historians, including Justin Pollard and Denis Mack Smith, thought Mussolini was probably aware of the assassination plot but that it was ordered and organized by someone else.

[17] Judge Giovanni Spagnuolo, in relation to the business clue linked to the Sinclair Oil agreement, added in his 1946 indictment - refuting it in detail - that this "hypothesis clashes with the most elementary logic".