The psychologists' union, an affiliate of the Confederation of Malta Trade Unions, said it would not participate in the protest over the hike in utility tariffs but left it up to members to decide whether to attend or not.
The Malta Union of Professional Psychologists is the first body to leave it up to members whether to participate.
Earlier this week, the CMTU said the planned street protest on the water and electricity tariffs would do more harm than good to the country, adding that its priority remained the generation of more employment opportunities and investment, especially at a time when the country was slowly emerging from the recession.
The protest is being organised by the Għaqda Unions Maltin along with the General Workers' Union and will be held in Valletta on Sunday.
The MUPP said it shared the CMTU's belief that, at a time when the country was struggling to emerge from difficult moments, the priority should be employment and investment.
It also believed in the process of social dialogue that should be open, transparent, genuine and respected every opinion on the weight of its own merits and not on the merit of who expressed it.
However, the MUPP said it also believed in freedom of expression and the fundamental right to stage peaceful protests, rights that were respected in the EU and in every country that believed in true democracy.
"A genuine and open dialogue process can help to prevent the need to protest. One does not exclude the other. History shows us that many times social dialogue occurred as a result of one protest or other."
When contacted, CMTU president William Portelli said the MUPP's decision demonstrated the democratic manner in which the confederation conducted its business.
"As a confederation, we never imposed anything on our members. As a confederation we took a stand agreed upon by all affiliates, but then it was up to the individual unions to take their own decisions and lead their own union. The CMTU does not interfere with its affiliates' internal discussions," he said.