Charities, religious groups and other organisations joined forces in a plea to Gordon Brown to take action to "protect civilians" as violence escalates in the Democratic Republic of Congo.

It is estimated that 5.4 million people have died as result of conflict in the African country since 1998.

In a letter to the Prime Minister, representatives of 20 organisations said: "Waiting for this crisis to escalate further would be disastrous.

"We call on you to show the necessary international leadership to ensure a rapid, short-term EU deployment, and for the UK to play whatever part is necessary to deliver that force, to fulfil the UK Government's promise to protect civilians."

According to the letter's authors, United Nations reinforcements are likely to take months to deploy and, in the meantime, Europe should implement a short-term deployment of troops to protect civilians.

"Such a force could immediately contribute to improving overall security in the area, and thereby improve access for humanitarian organisations and free MONUC (the United Nations Mission in the Democratic Republic of Congo) to fulfil its mandate in other areas.

"Most importantly it could save the lives of thousands."

Describing the situation as "a humanitarian catastrophe", the letter praises the British Government's "high-level engagement" over recent weeks and efforts in "supporting the political process to help bring an end to the conflict".

But the signatories say the ceasefire exists only in name and highlights the ongoing battles between the country's armed forces and rebel groups.

"Reports from the ground indicate that the situation is continuing to deteriorate, with attacks on civilians occurring every day," the letter states.

"Human rights organisations have documented the killings of at least 50 people in the town of Kiwanja, and it is likely there have been many more civilian deaths.

"Around 250,000 people have been displaced since August and humanitarian access to vulnerable populations is severely limited."

Praising Mr Brown's "significant leadership in the past by talking about the role that Britain should play in the world and the necessity to live up to our responsibility to protect civilians", the letter says: "This is a critical opportunity for you and the UK Government to show leadership in Europe, working with others to fulfil that pledge and act to prevent more killings."

The letter is signed by leading figures including Dr Muhammad Abdul Bari, secretary-general of the Muslim Council of Britain; Daleep Mukarji, director of Christian Aid; Kenneth Roth, executive director of Human Rights Watch; Christine Slower, acting general secretary of National Union of Teachers; and Barbara Stocking, chief executive of Oxfam GB.