Bonfires will also be organised by trade unions, who take the opportunity to promote labour rights, in Maribor, Koper, Ptuj, Murska Sobota and Gornja Radgona.

For the first time the Ljubljana event will be the result of a joint effort by the ZSSS, Pergam, KNSNS and KSJS trade union confederations, representing public as well as private sector workers.

They have chosen the motto of "We work together, we celebrate together" to stress the unity of the workers.

Jakob Počivavšek of Pergam told the press on Friday the wish was to overcome divisions among different groups, for instance the old and the young, private and public sector workers, those with regular and precarious labour arrangements.

Among the key challenges ahead, he highlighted the fight for decent work, collective bargaining agreements, pension reform and a different distribution of tax burdens.

Minister of Labour, Family, Social Affairs and Equal Opportunities Anja Kopač Mrak, on the other hand, pointed ahead of the holiday to continuing high unemployment and the widening gap between those with regular and those with "atypical" work arrangements.

"Which means a gap between regular work relationship and the concealed ones that should be treated as regular. This is unjust and unacceptable and is the result of abuse, manipulations as well as, in some parts, of open issues in legislation," she wrote in her Labour Day message issued yesterday.

Calls for better protection of labour rights also came from other organisations and bodies, such as Amnesty International Slovenije and Human Rights Ombudsman Vlasta Nussdorfer.

The ombudsman argued that the relevant state institutions have not been effective enough and that "grave violations continue to occur". In her message issued on Friday, she noted that foreign workers in Slovenia remain especially vulnerable to abuse.

A series of labour marked-related figures released by the Statistics Office ahead of the holiday showed that Slovenia had a 12.3% unemployment rate at the end of last year, when there were slightly over 112,700 registered unemployed.

The figures are worse for the young; the unemployment rate in the 15-29 age group rose by 10.8 points to 20.1% since when the economic crisis broke out in 2008.

While Slovenia has a 40-hour working week, workers in the country clocked in an average 39.3 hours a week in 2014, 1.2 hours down from 2008, while the EU average was 37.2 hours.

Pay data showed that since the economic crises broke out in 2008, the average net salary rose by 3.5% in real terms to EUR 1,013 last year.