The new federation brought together the Swaziland Federation of Trade Unions, the Swaziland Federation of Labour and the Swaziland National Association of Teachers.
Cosatu sent a delegation headed by first deputy president James Tyotyo, who addressed the congress at its official opening in Matsapha last weekend.
Tyotyo told the Tocuswa conference that the organisation should be the voice of the marginalised and fight forward for liberation.
He said that some of them would be devoured by the regime's forces but they should remember that their ideas and freedom would never be killed.
Cosatu international relations secretary Bongani Masuku noted that the establishment of Tucoswa mirrored the trend toward workers' unity throughout southern Africa, which is seeing unification efforts by Zambia's two federations ZCTU and FFTUZ and by four separate bodies in Lesotho.
"Our own experience against apartheid and the general struggle against capitalism taught us that only working unity is the decisive force against any and all forms of oppression and anti-worker regimes," Masuku stressed.
He pledged that South African trade unionists would be guided in their solidarity work "by the workers and people of Swaziland," warning against "tendencies towards petty bickering and divisive behaviours in some circles."
Emphasising that genuine Swazi patriots had only one enemy - the regime of despotic monarch Mswati III - Masuku urged Tucoswa "to take the front stage, claim your rightful space and lead the masses of Swaziland to a new and democratic society, working together with all your progressive allies."
The South Africa-based Swaziland Solidarity Network (SSN) also congratulated Swazi workers for choosing unity.
Spokesman Lucky Lukhele recalled the words of late South African communist intellectual Mzala Nxumalo on the foundation of the People's United Democratic Movement - Pudemo - that "a giant has been born" in Swaziland.
"True to comrade Mzala's words, another giant has been born in Swaziland and indeed that giant is the Trade Union Congress of Swaziland," said Lukhele.
"We as SSN are excited by progressives' efforts to isolate the regime and support the Tucoswa call for the boycott of the 2013 national 'selection' disguised as elections," he added.
"With this resolution it is clear that it is not going to be business as usual for the tinkhundla regime, because workers have spoken." Tinkhundla is the undemocratic system that vests all real power in the hands of the monarch while devolving administrative matters to traditional chiefs dependent on his patronage.
Lukhele also urged support for action planned by the Swaziland National Union of Students for March 21, when the organisation has undertaken to bring the country's two cities Manzini and Mbabane to a standstill in protest against tinkhundla,
Government propaganda head Percy Simelane slammed the decision to boycott next year's sham elections, insisting that it is an undemocratic thing to do. "They are offside with this. They are stepping on other people's rights," he protested.
Simelane insisted that next year's elections would be held in line with the national constitution of the kingdom, which is the supreme law of the land.
"We have no room for jungle law, hooliganism and dictatorial ideologies," he declared.
Tucoswa secretary-general Vincent Ncongwane, who gave his maiden speech at the end of the three-day congress, urged union members to do everything possible to frustrate the electoral farce.
Delegates agreed that if elections were to be held next year, they should be for a multi-party democracy and nothing else.
They plan to persuade the public against participation and will seek co-operation from political parties and civic society organisations, as well as faith-based and cultural bodies, to achieve a boycott.
"While we want the multi-party elections, we need to be realistic and we need to go to the rural areas too," said Ncongwane.
He dismissed Simelane's complaint, asserting: "Only our membership can tell us we are offside when we say we will boycott next year's elections and advise others to do the same."
The secretary general also denounced government mismanagement of the economy and its devotion of huge amounts of money to an army that fights no-one but the people.
"That is the problem with idle hands, yet we have a problem with our public health facilities and HIV," he complained.
The Mswati regime has been in dire straits because of royal family profligacy and has had difficulties paying public service salaries.
It was offered a loan by South Africa last August in return for progress towards democracy but rejected conditionality, protesting that this would mean legalising political parties, which were banned in 1973.
However, campaigners believe that the condition is being evaded with loan money finding its way into Swaziland disguised as Southern African Customs Union revenues.
The rationale behind this would be Pretoria's reluctance to see the Mswati autocracy implode into chaos with a subsequent mass flight of refugees into South Africa, as has happened with Zimbabwe.
Swazi trade unionists are intent on acting with discipline and determination to bring about democratic change that will avoid chaos while bringing the monarchy to heel.