(VIENNA) - Austrian President Heinz Fischer on Monday put his signature to the Lisbon Treaty aimed at reforming decision-making in the expanded European Union, formally ratifying the document.

His signature was the final step in the ratification process, after the EU treaty was approved by the council of ministers and both houses of parliament.

Fischer said he had signed the treaty "after conscientious examination of all the factors"

Critics in Austria have staged protests against the treaty with several thousands marching in the street and more than 100,000 people signing a petition, demanding a referendum on the document.

Over the weekend, protesters again called on Fischer not to sign the treaty, which some say would violate Austria's neutrality.

Fischer rejected the claims Monday, however, adding that the new treaty was "practically identical in content" to a draft constitution rejected by French and Dutch voters in 2005, that Austria had "ratified without any problems or concerns."

The Lisbon Treaty must be ratified by all 27 EU members before it can come into effect in 2009, as planned. Only Ireland is putting it to a referendum, due to domestic constitutional obligations.

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