David Cameron said he believes in low taxes for businesses because he wants "Britain to be a winner in the global race" but said it was important to make sure companies pay what they should.
The Prime Minister spoke as he arrived at an European Union summit in Brussels.
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Armed police have carried out a raid apparently linked to Wednesday's deadly terror attack in Westminster.
Cheryl Grimmer vanished from inside a beach shower block in Wollongong, Australia, in 1970, when she was just three.
Pc Keith Palmer was on the front line and because of his actions, the Westminster attacker was unable to kill anyone else.