The new EU Reform Treaty is effectively the same as the constitution it was designed to replace, according to a leading architect of the constitution.
Mr Giscard d'Estaing says the treaty is "impenetrable for the public"
The treaty differs from the abandoned constitution in "approach rather than content", says former French President Valery Giscard d'Estaing.
Mr Giscard d'Estaing led a committee drafting the constitution, rejected by French and Dutch voters in 2004.
Several European governments hope to avoid a referendum on the new treaty.
In an article in the UK newspaper, The Independent, Mr Giscard d'Estaing says the treaty makes important concessions to the UK.
The UK, alongside Denmark and The Netherlands, is among the countries whose governments oppose a referendum.
Mr Giscard d'Estaing points out that the UK will not be bound by the treaty's rules on human rights and judicial harmonisation, and would retain the right to "duck in and out of the system as it pleases".
British Euro-sceptics want the government to hold a referendum on the treaty, arguing it is no different to the constitution.
However, the government of Prime Minister Gordon Brown wants the treaty to be passed by parliament alone.
Mr Giscard d'Estaing says the "proposed institutional reforms" of the rejected constitution can still be found in the new treaty.
The authors of the new treaty, he says, have taken the original draft constitution and "blown it apart into separate elements".
They have then "re-attached them, one by one, to existing treaties".
Changes to the original constitution - such as jettisoning references to a European flag and anthem - were made to "head off any threat of referenda", Mr Giscard d'Estaing says.
The EU Reform Treaty was agreed earlier this month at a summit in Lisbon, Portugal.
The document aims to streamline decision-making within an enlarged EU of 27 member nations.
It was written to replace an EU draft constitution that was overwhelmingly rejected by French and Dutch voters in 2004.
In his article for The Independent, Mr Giscard d'Estaing says the treaty was drafted by legal experts in a process very different from the "public" debates that yielded the constitution.
He describes the treaty as "a catalogue of amendments" that is impenetrable for the public.