Addressing a press conference at the union office in Mombasa, Mr Sang said his members were not opposed to the concession but had questioned how it was being pushed down the throats of the stakeholders, leading to an uproar.
The uproar against the planned concession started last month when KPA invited bids from private firms for Mombasa port berths 11 to 14, and container terminal 1 and Lamu's berths 1 to 3, and the development of a special economic zone.
These provoked Coastal leaders led by Mombasa Governor Abdulswamad Nassir to oppose the privatisation plan.
The other leaders were Changamwe MP Omar Mwinyi, Jomvu MP Badi Twalib and Mombasa Senator Mohamed Faki.
But KPA chairman Benjamin Tayari denied claims there was a move to privatise the port, insisting that the government wanted to lease out the port services to investors who would add value to the public assets.
President William Ruto has assured the stakeholders that the two ports were not being privatized but some services were being concessioned to expand port services and create employment.
Azimio leader Raila Odinga called for public participation before any concession was done and wondered why there was a mystery in the ongoing process.
Yesterday, Mr Sang said leaders were right in expressing their worries because the government had not done public participation to explain the extent of the leases and their value to workers and Kenyans at large.
"The question the members are asking is whether we should first do public sensitization through structured and strategic for all stakeholders comprising KPA, county government, Dock Workers Union, local community and other stakeholders," said Sang.
He said the government should also find out how to explain to the public the difference between privatization and concession of port facilities and convince them about the benefits.
"We are also asking the politicians what they meant in 2017 and 2022 when they were going around during their campaign and promising to establish Dubai in Kenya," he said.
Sang said for the country to create more jobs, it must invite investors to expand industrialization.
"No country in the world has created jobs without industrialization, and in our view, this is what the government is trying to do," said Sang.
The union boss who was flanked by members of the executive committee, asked the ministries of Transport and National Treasury, to organise a seminar in Mombasa and explain to stakeholders why the government wants to lease the port services to private firms.
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"We recommend a three-day seminar on this subject before we ask ourselves whether concession is good for us or not," said Sang.
He decried the politicization of the issue and regretted that the port stakeholders could lean towards the decision of politicians.
"Our fear as a union is the politicization of the issue. That is why we would want not to be misunderstood by our stakeholders," said Sang.
He blamed the government for inviting the bidders to bid for services at the port before conducting a wider consultation, raising the alarm.
Sang said the idea could be good, but how it was being pushed was what was causing the problem because most people do not understand the meaning of concession.