A new hourly rate of £2.50 was introduced at the same time for apprentices, who previously did not qualify for a statutory wage. The age threshold for paying the adult rate will be reduced from 22 to 21, giving an estimated 50,000 people a pay rise of more than 20%.
To mark the increase, the Government announced that employers who deliberately flouted minimum wage laws will be publicly named under a new scheme.
Liberal Democrat Employment Relations minister Ed Davey said: "Bad publicity can be a powerful weapon in the fight against employers who try to cheat their workers and their competitors. Their reputation can be badly damaged if they are seen to be flouting the law.
"Responsible employers should also make themselves aware of the new rates that come into effect today. The increases to the national minimum wage this year are appropriate for the economic climate. They will strike a balance between helping the lowest paid whilst at the same time not jeopardising their employment.
TUC general secretary Brendan Barber said: "This increase will put extra cash in the pockets of some of the UK's lowest paid workers and today there are also significant gains for apprentices and young workers."