Watch: Climate activists make a bloody mess in protest fail

Climate change activists have been left red-faced after an attempt to raise awareness of the "climate emergency" went wrong in London.

Extinction Rebellion activists used an out-of-commission fire engine to drench the front of the Treasury building in red liquid but lost control of the hose in chaotic scenes captured on camera.

The protesters chased the hose to try and grab it but were not able to regain control, sending 1800 litres of fake blood spraying all over the street.

The hapless activists even ended up spraying themselves before four people were arrested by Metropolitan Police on suspicion of criminal damage.

Extinction Rebellion protestors demonstrate outside the Treasury building in London. Photo / Reuters

One demonstrator said the liquid was simply red food dye mixed with water and could easily be washed off.

They also erected a banner reading "Stop funding climate death".

The group's protesters have succeeded before in disrupting life in the capital in hopes of gaining attention to their cause.

In April, they blocked several London roads and bridges during 10 days of action designed to alert the public and politicians to the "climate emergency".

Extinction Rebellion climate activists stand on a fire engine outside the Treasury building in London. Photo / AP

Britain aims to achieve net zero carbon emissions by 2050, but Extinction Rebellion wants it done by 2025.

A spokesman for the group said: "It is time to imagine a future where humans no longer cause irreparable harm to themselves and their surroundings, but recognise and support the interconnectedness of life in its broadest sense."

The group said the protest was designed "to highlight the inconsistency between the Government's insistence that the UK is a world leader in tackling climate breakdown, while pouring vast sums of money into fossil exploration and carbon-intensive projects".

- Additional reporting, AP