London - Britain on Thursday formally ratified the European Union's Treaty of Lisbon, the country's Foreign Ministry said in London.

All steps for the final ratification were taken and the documents were deposited in Rome, where the 1957 Treaty of Rome for the founding the European Economic Community was signed.

Both houses of the British parliament as well as the head of state Queen Elizabeth II okayed to the reform treaty.

Britain was considered a "swing candidate" as far ratification went. After Ireland rejected the reform treaty in a referendum on June 12, there were calls among eurosceptics in Britain as well for a referendum on the issue. (dpa)