Doubts have been raised about the value of the European Union constitution by one of its authors, two weeks before it is put to the vote in France.
Ms Stuart said the treaty was not necessary for EU enlargement
The government says the treaty, an EU rule book, will streamline decision making following its enlargement.
But Gisela Stuart, a Labour MP who helped draft the constitution, says it could hold back economic reform.
To become law, it needs to be ratified by all member states. If the French vote no, there may no UK referendum.
The French are due to vote on 29 May - polls suggest the "yes" and "no" vote campaigns are neck and neck.
But Ms Stuart, MP for Birmingham Edgbaston, said if the constitution were not approved - it need not damage the European project.
She told the BBC the treaty was not necessary for EU enlargement, the EU would continue to operate and any bureaucratic changes could be agreed by heads of government in a separate treaty.
And she added: "It doesn't address the fact that the European Union, in a globalised world, has to look at the way it delivers economic success for the people of Europe."
She added that if French voters were committed pro-Europeans like her, they should ask themselves whether the document was good enough for their vision of Europe.
The latest opinion polls in France and the Netherlands suggest that the result of referendums due on 29 May and 1 June are balanced on a knife-edge.
So far six countries have ratified the constitution, while Austria, Spain and Belgium are not far behind.
The German, Belgian, Estonian and Latvian parliaments are expected to ratify the constitution this month.
The UK is expected to hold a referendum on the constitution in spring 2006.