The French and German governments have recommended that their nationals pull out, and 800 Russian workers have been evacuated.
A spokesperson for Halcrow, an engineer working on 48 emergency reconstruction projects in Basra, said UK guidelines had not changed.
He said there was no official recommendation to evacuate so the firm would remain where it was.
The spokesperson said: "We continually review what we are doing in Iraq. Things are going ahead as planned – certainly at the present moment we are not going to change anything."
However, the Coalition Provisional Authority South did shut the gates at its compound in Saddam Hussein's former palace in Basra for one day this month while heavy rioting was going on.
A spokesperson for contractor Amec, which has won nearly £1bn of work with US contractor Fluor, said the firm had five staff in Iraq. He said they were all well guarded by private security as well as coalition protection. They are working on the early design phases of projects.
Stuart Doughty, chief executive of Costain, said he did have some fears over the safety of staff in Iraq even though the contractor is working on an infrastructure masterplan in Kurdistan, northern Iraq, where the security situation is less threatening.
Doughty said: "We are not pulling out – not at the moment. Our involvement is relatively discreet – we have three or four people behind the scenes working with ministries. They are not on the ground. Some of the work is being done from the UK. But it is causing me great concern."
However, UK consultants that had considered going to Iraq have started to have second thoughts. Babtie chief executive Bill Mitchell said last year that it would pitch for work but this week ruled itself out.