Interim results for the six months to June 30 show pre-tax profit down to £1.4m from £3.2m last time as turnover ticked up to £92.6m from £85.7m.
Chief executive Mark Lawrence said: “In the short term, there continues to be immense pressure on margins.
“In many instances the number of bidders for projects remains excessively high, which can lead to the project being awarded at an unsustainable level.
“We have been reluctant to become involved in such bidding wars.”
T Clarke continues to diversify away from traditional contracting and is expanding in the facilities management and green energy sectors.