Rubber bullets may be used at the tuition fees protest on Wednesday in cases of "extreme" disorder, which would be the first time they have been fired on British mainland soil.

More than 4,000 police are preparing to take to the streets to ensure public order is maintained after last year's demonstrations turned violent. Officers from forces around the country will be deployed to the capital as "mutual aid".

Commander Simon Pountain said criminal behaviour would be dealt with "decisively and swiftly", and rubber bullets would be available for use. Baton rounds would be deployed in "extreme circumstances", a spokesperson for the Metropolitan Police Service (MPS) confirmed.

"MPS officers are deployed to facilitate peaceful protests and that is the aim. There are a range of tactics available if there is criminality and violence associated with the event. One of these is the authority to deploy baton rounds in extreme circumstances", the spokesperson said.

They added the batons were only carried by a "small number of trained officers" and would not be held or used by the officers policing the protest route on Wednesday.

"To give context to their use, the MPS had authority to use baton rounds during the disorder this summer but did not do so."

Although the rounds, also known as "rubber bullets", have never been used on mainland Britain, they have been linked to deaths in Northern Ireland. The bullets are designed to cause pain but minimise injury.

Baton rounds were pre-authorised for use at the summer riots, although were never actually used by police forces.

Jenny Jones, a Green Party member of the Metropolitan Police Authority and London Mayoral strongly disagreed with the plans.

"Any officer that shoots a student with a baton round will have to answer to the whole of London," she said.

"The prospect of the police shooting at unarmed demonstrators with any kind of bullet is frankly appalling, un-British and reminiscent of scenes currently being used by murderous dictatorships in the Middle East."