A group of Czech senators has filed the second constitutional challenge against the Lisbon Treaty on European Union reform. The papers deposed in Prague by Senator Jiri Oberfalzer will add to jitters among the treaty’s backers. They are already on tenterhooks about Ireland’s second referendum — to be held this Friday.The senators’ court move is likely to further delay the treaty’s signing by Czech Treaty critic President Vaclav Klaus. The move prompted speculation that the senators were stalling until next year’s general elections in Britain, which could result in a referendum on the treaty there. The signing by Klaus would seal Czech ratification; Poland is also yet to ratify, where its president is also Euro-sceptic. The Irish rejected Lisbon last year. All but three of the European Union countries have completed ratification but if Ireland votes ‘no’ again, the treaty might not survive. Klaus has said he is not worried, because he expects another Irish rejection.