The terms of reference of a public inquiry into spy cops were published last week.
The Tories set up the inquiry following a series of revelations that included how undercover officers spied on the family of murdered teenager Stephen Lawrence and other grieving families.
They also formed long-term relationships with female campaigners.
The inquiry, overseen by Lord Justice Pitchford, is set to run for three years. It will look into the role of undercover policing of political campaign groups and social justice groups.
The Blacklist Support Group represents workers who construction bosses put on an illegal database with cops’ help.
It said, “The concerns of thousands of trade unionists must be heard and must be investigated.
“Pitchford may not get the full story of state surveillance on trade unions but an opportunity like this only comes along once in a generation.
“After decades of campaigning, we cannot tolerate a whitewash.”