Organisers TUC expected around 100,000 people to take part in the March for the Alternative, just weeks before sweeping welfare cuts kick in next month.

More than 4,500 police officers are keeping order along the march route amid fears that the protests could be taken over by violent anarchists.

The TUC was keen to stress that the march would not see a repeat of the violence that marred protests over university fees.

TUC General Secretary Brendan Barber said the march would be “good-natured”.

In an address to protesters later today, he is expected to say that the spending cuts will “hammer” crucial services and hit the poorest and the most vulnerable hardest.

The TUC is angry at cuts in funding to the NHS in particular and has expressed concern over the potential job losses in the health service, expected to number around 50,000.

Mr Barber is also expected to call for the adoption of the so-called ‘Robin Hood’ tax – or unilateral financial transaction tax - a proposal supported by several Churches and Christian groups, including The Salvation Army, the United Reformed Church, CAFOD, Tearfund and Christian Aid.

Christians are taking part in the march, among them members of the URC, the Roman Catholic National Justice and Peace Network, the Student Christian Movement, Housing Justice, and Church Action on Poverty.

CAP said it wanted the Government to tackle the budget deficit in a “fairer” way.

The charity’s coordinator, Niall Cooper said: “It is becoming clearer every day that the Government’s public spending cuts are falling unjustly on the poorest and most vulnerable people in society.”

Before the march got underway, Christian campaigners held a service of commemoration for Archbishop Oscar Romero, who was a vocal advocate for the poor in El Salvador until his assassination in 1980.