The French prime minister, Lionel Jospin, has made his first keynote speech on the future of the European Union since coming to office four years ago.

His strongly-socialist contribution to the growing European debate diverges from Germany's vision, placing a similar emphasis to Tony Blair on giving a greater role to the national parliaments of member states in the EU's affairs.

But the speech has also been seized upon by eurosceptics, with calls by Jospin for a European constitution, "economic government" of euro-zone countries and a "social treaty" taken by them as "proof of the EU's centralising agenda".

Jospin called for a Europe of economic solidarity - "to be more than just one market in a sea of globalisation" - with the euro-zone going beyond being a mechanism for stability to become an "economic government".

Calling for "action to stop any behaviour detrimental to the European interest", Jospin revived the recent row over tax harmonisation.

"Combating 'tax dumping' is one immediate priority, it is not acceptable for certain member states to practice unfair tax competition in order to attract international investment and offshore headquarters of European groups. Ultimately, the corporate tax system as a whole will have to harmonised," he said.

Jospin went on to observe that the EU could not be "merely a free trade zone" calling for a "social treaty" to make economic cohesion serve social solidarity.

"Working conditions must be harmonised upwards...A genuine body of European social law, establishing ambitious common standards...We must aim for a European social treaty," he said.

On the federalist agenda - often most associated with Germany - Jospin backed the idea of a "federation of nation states" or "a gradual controlled process of sharing competences or transferring competences to the Union level".

Falling short of backing Tony Blair's call for a second chamber to the European parliament made up of national MPs, Jospin argued for a permanent conference of national parliamentarians to prevent Europe encroaching too far into member states' sovereignty.

This would be the backbone of a "federation of nation-states" which the French premiere said was necessary in an enlarged EU in which improved cooperation would be indispensable.

Shadow foreign secretary, Francis Maude, responded to the speech by accusing Jospin of seeking to take Europe backwards to a protectionist and outdated socialist super-state.

"Mr Jospin is setting out an agenda where more and more powers are passed out of the hands of nation states such as Britain. This is a backward-looking blueprint for an outdated socialist superstate. This is an agenda for a protectionist Europe closed to the rest of the world, for harmonised company taxes and more red tape which will raise still further the EU's high unemployment levels," said Maude.

Commission president, Romano Prodi, will keep Europe on the agenda with a speech on Tuesday outlining the future role of the European commission.