The Nigerian senate has passed a modified version of a bill designed by President Olusegun Obasanjo to curb the power of the trade unions.
The unions have forced the government to reduce fuel price rises
But it amended a no-strike clause so that it only applies to those working in essential services.
Union leaders say they believe the reform is intended to break down opposition to the government.
If the bill does become law in its current form, it will still make membership of trade unions voluntary.
"The Senate is yielding to the demand of labour, by amending certain original demands made by the president, " senate spokesman Henry Ugbolue told Reuters news agency about the no-strike clause.
Over the past year the unions' umbrella organisation, the Nigerian Labour Congress (NLC) has called three crippling general strikes against fuel prices rises.
The Nigerian police last month prevented the NLC from holding a demonstration against the bill's proposals, which will end its status as the representative of all Nigerian trade unions.
Before becoming law the measure needs to be approved by the lower House of Representatives, and can be vetoed by President Obasanjo.