The trades-based organizational model, which continues today especially in the building and construction industries, is based in older European traditions that can be traced back to guilds.

However, with industrialization came the creation of a new group of workers without specific trades qualifications and, therefore, without ready access to the representation offered by the TLC's affiliates.

[citation needed] The growth of industrial jobs in the first half of the 20th century, combined with new legislation in most Canadian jurisdictions explicitly recognizing the industrial union organizational model, led to fears of raiding between the unions belonging to the two federations, the TLC and the CCL.

[citation needed] In January 2018, Unifor, the largest private sector union in Canada, left the CLC to become independent.

[3] The CLC accused Unifor of leaving the congress in order to raid an affiliate union, UNITE HERE Local 75, in Toronto.

[citation needed] Under the general labour relations laws in effect in all Canadian jurisdictions, groups of workers deemed "appropriate for collective bargaining" may vote to join a union.

Only in rare cases groups of workers with collective bargaining rights can be "directly chartered" as locals of the CLC.

Local unions of Canadian labour organizations may affiliate to the CLC and pay the required per capita fees.

Many Canadian labour organizations have, at their own conventions, established policies, by-laws or constitutions requiring local unions to affiliate to the CLC.

[citation needed] The CLC has also chartered approximately 130 district labour councils (DLC), based upon municipal jurisdictions.

Local unions with membership within the county, region or city of the DLC may affiliate and participate in the labour council.

These councils assist with provincial or national political or issue campaigns and also lead efforts in municipal elections.

[citation needed] The CLC has head offices in Ottawa out of which it runs the Congress of Union Retirees of Canada.

Field workers based in these offices assist DLCs and their political and issues campaign[citation needed] Since 1994, the CLC has been a member of the Halifax Initiative, a coalition of Canadian non-governmental organizations for public interest work and education on international financial institutions.

[citation needed] The Trades and Labor Congress of Canada (TLC) held a policy of non-partisan activity right up until the formation of the CLC.

NDP constitution also recognizes the CLC's District Labour Councils, organizations of local unions in a single city or town, as delegating bodies to the conventions of the provincial and federal New Democratic Party sections.

[citation needed] Since the foundation of the NDP, and particularly since the 1980s, the labour movement's relationship within the social democratic left has changed in two ways.

First, unions increased their involvement with social coalition groups such as organizations advocating for women's economic rights, peace or other causes which have an avowedly non-partisan orientation.

At the outset of the election campaign, several unions had established partnerships with organizations such as The Council of Canadians in order to attempt to derail the Progressive Conservative government's Canada–United States Free Trade Agreement.

These social coalition groups and the Liberal Party made opposition to the Free Trade Agreement the focus of their campaign efforts.

While the NDP attained what was then their best result in the party's history (they would win more seats in the House of Commons in the 2011 and 2015 federal elections), some union leaders publicly criticized the NDP leadership immediately after the election for not being sufficiently focused on opposition to the Free Trade Agreement.

[citation needed] Since that election, the tactical nature of the relationship between some unions and the NDP has further degraded to their point where the Canadian Auto Workers Union (CAW), the successor to the Canadian section of the UAW has, since the late 1990s, supported the Liberal Party federally and in Ontario provincial elections.

Nonetheless, other significant unions remained steadfast in their support with the NDP and the Bloc Québécois as their top political priorities, even while maintaining involvement in social coalitions.

[citation needed] The Canadian Labour Congress established April 28 as the National Day of Mourning to workers killed and injured on the job.