The move follows an investigation by the BBC’s Newsnight programme into site conditions in the country.
Foreign workers told the programme they have had their passports confiscated and are forced to live in conditions “not fit for humans”.
The working day is said to last from four in the morning until six at night while recruitment agencies take half of workers’ wages for lodging and expenses.
Carillion is working on phase 1B of the Downtown Doha project – a mixed-use development comprising retail, commercial, residential, leisure, cultural and community facilities.
A Carillion statement said: “We do everything we can to safeguard the health, safety and wellbeing of our people in Qatar, including employees of our subcontractors.
“As a leading support services and construction company, Carillion sets best in class standards for our people’s health, safety and working conditions wherever we work.
“Carillion is deeply concerned and surprised by the claims made by Newsnight concerning one of our subcontractors and one of their sub-suppliers in the programme broadcast on the 8th December.
“We are conducting an immediate review of these claims to establish the position and take appropriate action.”