The Foreign Secretary was attacked by the Liberal Democrats for failing to block moves by the Department of Trade and Industry to support British firms involved in the scheme. Mr Cook was criticised earlier this week after he confirmed that Indonesia had used British-built jets to intimidate separatists in East Timor.
Menzies Campbell, the foreign affairs spokesman for the Liberal Democrats, warned that the Ilisu Dam project on the River Tigris could ruin the environment, leave thousands of Kurds homeless and trigger the world's first "water war" by disrupting supplies to Iraq and Syria.
Balfour Beatty, one of the firms contracted to help build the dam, is in line for help from the DTI's Export Credit Guarantee Department.
t Mr Cook said yesterday that he would push for Turkey to be granted candidate-nation status for membership of the European Union.