Colin Adams, chief executive of the British Consultants and Construction Bureau, said that many UK firms had enough experience in Iraq to carry out infrastructure work.
He said it would be "remarkably stupid" of the government and the US to ignore that expertise.
The bureau is worried that major rebuilding contracts, valued at about £600m, will be awarded to US firms. The US uses "tied" aid packages to ensure that its own companies are awarded rebuilding work.
The US government has announced a package or rebuilding work worth $900m (about £600m), for which it drew up a shortlist of five US firms.
Adams said: "I think it is likely that the major opportunity for UK companies will be through the opening up of subcontracts.
A further concern for the bureau is that consultants and contractors that have recently left Iraq might return after the invasion to find that companies from other countries have taken over the contracts they had been carrying out.
Adams said that this occurred in Kuwait after the Gulf war.
"The hope is that the US will acknowledge how much support we have given them and open bidding for subcontracts to the UK industry – a kind of moral pressure on the US."
It is understood that Blair did not raised any commercial concerns with the US government before giving British support for the US invasion.
The bureau's list comprises 75 companies from all sectors of British industry, about half of them in the infrastructure sector. Consultants included are believed to include Atkins, Mott MacDonald and Arup.
Some contractors are known to have approached the Office of the Deputy Prime Minister directly.