London  - The British government Thursday criticised Sudan for retaliating against international aid workers following the arrest warrant issued against President Omar al-Bashir.

Aid organizations have warned that millions of lives would be put at risk by al-Bashir's decision to expel 10 humanitarian groups from the Darfur region, including Oxfam, Save the Children, Care International and Doctors Without Frontiers.

Deputy Labour Party leader Harriet Harman, standing in for Prime Minister Gordon Brown, told parliament that it was important that Sudan should not "retaliate" against the agencies and refrain from "escalating" the situation.

In Ireland, Foreign Affairs Minister Michael Martin urged the Sudanese government to reverse its decision which amounted to using "extremely vulnerable people as pawns."

Al-Bashir Wednesday became the first sitting head of state to be served with an arrest warrant for war crimes by the International Criminal Court (ICC) in The Hague, a move that has sparked anger, protests, and rallies of suppport in Sudan.

Oxfam and Save the Children said they would appeal against the decision to withdraw their licences for operations in Sudan.

Penny Lawrence, Oxfam's International Director, said the withdrawal of its registration would affect more than 600,000 people who were being given "vital humanitarian and development aid, including clean water and sanitation on a daily basis."

Of those, 400,000 were affected by the ongoing conflict in Darfur where people continued to flee from violence and the humanitarian needs remained "enormous."

Oxfam GB has operated in northern Sudan since 1983 and currently has 450 staff there, 90 per cent of whom are Sudanese. (dpa)