Supportive of Francisco Franco,[1] Belton however opposed Eoin O'Duffy taking an Irish Brigade to Spain, feeling that they would be needed in Ireland to counter domestic "political ills".

[2] In 1905, he was present at the establishment of Sinn Féin in London, and in November 1909, according to some sources, he initiated Michael Collins into Irish Republican Brotherhood (IRB).

A detailed narrative of his activities during the 1916 Rising is contained in a handwritten letter he sent in 1937 to Máire English, supporting her claim to a Military Service Pension.

[5] In the eight-seat constituency, he was the third person to be elected, after Kevin O'Higgins (of Cumann na nGaedheal), who would be assassinated one month later, and Bryan Cooper.

Fianna Fáil, which had been founded in 1926 by Éamon de Valera, contested Free State elections but its policy was to refuse to take seats in the Dáil; this was because the Oath of Allegiance, agreed in the Treaty, required all TDs to swear, inter alia: "I will be faithful to H.M. King George V, his heirs and successors …" The 5th Dáil first met on 23 June 1927.

[6] The next day's paper quoted him as saying that he was taking his seat in the hope of saving the nation "from the degradation and destruction" which he believed the passage of proposed new legislation would involve.

On 11 August, de Valera and the 42 other Fianna Fáil TDs altered their policy and decided to take the Oath, characterising it as "merely an empty political formula".

[citation needed] Belton joined Cumann na nGaedheal in 1933 and was returned as a TD for Dublin North at the 1933 general election.

[11] Despite these claims, the organisations' ideological leanings soon became apparent: When our organisation's work is complete we will make Ireland a very hot spot for any communist to live in … if it is necessary to be a fascist to defend Christianity then I am a fascist and so are my colleagues.The ICF would hold pro-Catholic and anti-communist rallies, drawing an estimated crowd of 40,000 on one occasion, and would seek to publicise the massacres committed by the Spanish Republicans.

In November 1936, Belton travelled to Spain to arrange for a shipment of medical supplies to be purchased with funds raised from church-gate collections.

[12] During this time, Belton began openly engaging in antisemitism: We hear the boasting coming from the Government Benches, we heard it today, of the progress of industrialisation.

I suggest that Jews have been the propagandists of Communism the world over, and we should not let them into sheltered trades and positions in this country to carry on their propaganda.The ICF's popularIty would dwindle following Belton's loss in the 1937 general election, as well as its inability to change the government's policy on Spain and in the face of heavy casualties suffered by O'Duffy's volunteers.

In 1937, he was active building several hundred houses at Belton Park, part of Puckstown Lane, which he renamed Collins Avenue.

Reporting to the October 1937 Special Convention of the ICF, the organisation's honorary secretary stated that in April Belton "suffered from a severe breakdown in health caused by overwork, principally his efforts on behalf of the Irish Christian Front, and more especially by hardships undergone by him through his journey to Spain.

– Irish Press (26 November 1936) "I have never been a party politician in the sense that I would obey the orders of any political junta who would tell me to do a thing, whether I considered it right or wrong."