Balfour Beatty is a member of the Metronet consortium bidding for part of the £7bn Tube refurbishment and maintenance programme.
The protesters, led by the London regional council of rail union RMT, will be joined by groups opposed to the construction of the Ilisu dam in Turkey. Balfour Beatty is leading a consortium to build the £1.25bn project.
Speaking at the conference fringe meeting addressed by London mayor Ken Livingstone, RMT assistant general secretary Bob Crow said: “How can you have major building firms running the Tube network? It doesn’t make sense.”
Leaflets for the demonstration are headed “Keep scum contractors off the tube”. Its organisers said they expected more than 1000 demonstrators.
A spokesperson for Balfour Beatty said the group had the right to protest.
The firm received another blow on Tuesday after Skanska pulled out of the consortium to build the Ilisu dam.
The spokesperson said the consortium’s position was unchanged by the move. She said: “Skanska’s decision to pull out of the consortium was based on certain aspects of the contractual negotiations being unacceptable to their general commercial approach. The decision is not in any way related to the environmental or resettlement issues, which are still under review.”