FOUR protesters were arrested yesterday after anti-austerity campaigners took to the streets of London to demonstrate anger at the new Conservative government.

Police said one police officer and one member of police staff were being treated in hospital after being injured during the "unplanned anti-austerity protest".

Officers were also investigating after the Women's War Memorial in Whitehall was defaced with graffiti which said "F**k Tory scum".

The crowd of protestors was met with a large police presence after gathering outside Conservative campaign headquarters in Westminster, where David Cameron had issued a rousing speech to party activists little over 24 hours earlier.

Police said an estimated crowd of 100 people had gathered outside Tory HQ before moving on to Downing Street.

Activists chanted "get the Tories out" and Whitehall was shut for some time during the demonstration.

John Sinha from Occupy Democracy, one of the groups taking part in the protests, said: "David Cameron will have no popular mandate for his vile attacks on the poor and this demonstration shows that the British people intend to fight back."

A statement from Metropolitan Police issued last night said: "Four people have been arrested for a variety of offences under the Public Order Act, 1986.

"Officers are aware of criminal damage to the Women's War Memorial in Whitehall and are investigating.

"There are no reported injuries to any members of the public."

It added: "One police officer and one member of police staff have been injured policing this protest. Both are being treated in hospital. The officer is being treated for a suspected dislocated shoulder. The member of police staff is being treated for a cut lip after being struck by an object."

In Cardiff, around 200 people gathered at the city's statue of Labour politician Aneurin Bevan, who is best known as the chief architect of the NHS.

Former pop singer and opera star Charlotte Church was among those taking part. She addressed the campaigners and carried a placard which said: "I'm mad as hell and I'm not going to take it any more."

She told the crowd the UK had "masochistically condemned itself to five years of Tory rule" with "nothing to stop them from destroying our welfare system, selling off our health service, and even making constraints upon democracy.

"This is a government that does not care about its people and is only interested in cosying up to big business," she added.