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This is the moment a cop was left with a bloody gash on her face after being hit by a flying beer can during today's protest against David Cameron .

Thousands of demonstrators descended on Downing Street this morning, calling for the PM to step down in the wake of the row over his personal finances.

They waved placards with the slogans 'Time to go, chum' and 'He's got to go', while one even paraded a pig-shaped piñata with Cameron's face on it.

But as the day went on, the protest descended into violence, with police officers pictured locked in clashes with protesters near Big Ben.

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(Image: WENN)

(Image: WENN)

One female cop was left with a streak of blood on her cheek after a can of Fosters was apparently hurled toward her.

A picture of the incident shows the officer reacting as the can is thrown in her direction, sending droplets of beer flying through the air.

Other photos show demonstrators scuffling with officers in central London as they called for Cameron's resignation.

Some protesters turned up wearing pig masks and pig noses, with others sporting tropical shirts and flower garlands in reference to the Panama Papers.

(Image: Rex) (Image: WENN)

Singer Lily Allen was also spotted amongst the crowd, and she live-tweeted a series of comments and photos from the march using the hashtag #resigncameron.

One snap showed a campaigner wearing a pig mask and a selfie of the blue-haired singer wearing reflective sunglasses and a leopard-print bandana.

She tweeted on Friday: "I will be protesting at no10 tomorrow, unless of course he resigns before then. You should too, #resigncameron".

Other banners read "Cameron is a little slug - weasel", "Get the Tories out", and "Eton's Mess".

(Image: WENN)

Calls for Mr Cameron's resignation have been mounting since it revealed he had shares in the offshore trust set up by his late father, which he sold before becoming prime minister.

Following criticism for not making the declaration sooner, he confirmed he would publish his tax returns, accepting blame for the controversy.

Labour leader Jeremy Corbyn has called for the Prime Minister to make a formal Commons statement on the issue, claiming Mr Cameron had 'misled the public' and 'lost the trust of the British people'.