The European Commission should remain central to the EU's policy-making process, a senior commissioner said on Friday.

Sparking a new storm over the future of the EU, Frits Bolkestein, the internal market commissioner, called for a continued role for the unelected commission. His comments came as many within the EU move to shift the balance of power from the commission to council meetings of EU government ministers.

Bolkestein warned: "The Nice European council marked a turning point in many respects by revealing the dangers threatening Europe if we do not opt for a clear and effective decision-making process".

In an attack on the new post-Nice "inter-governmentalism", favoured by countries including the UK and Sweden, the Dutch commissioner said: "The efficiency of inter-governmental decision-making is in inverse proportion to the number of member states around the table. The bigger the group, the more limited its decision-making powers become. Legitimacy is undermined in the absence of effectiveness. The EU will lose its moral basis if it cannot reach decisions."

Rejecting inter-governmentalism and the concentration of powers in the hands of the council of ministers at the expense of the commission, Bolkestein is seeking to reinforce the "community method". He argued: "The commission will have to play a pivotal role in all the areas to which the EU assigns the status of common interest. It will therefore have to be effective, thorough and bold, not a group of ambassadors but the heart of the community."

Referring to a "shifting balance of influence between member states" and the creation of different coalitions on different issues, he outlined "the particular challenges" facing the EU - which included delivering the Lisbon agenda to make Europe the most competitive economy within 10 years, enlargement, a clear definition of foreign and security policy and a policy on asylum-seekers and immigration.

Responding to the commissioner's speech, Denis Macshane, an aide to the minister for Europe Keith Vaz, said: "Europe has to have as much integration as necessary to make reform and the single market work. But as Joschka Fischer said in his London speech it is the nation state that provides the main source of democratic legitimacy for the EU. It is foolish to get into a completely false argument between integrationists and anti-integrationists.

"The commission should concentrate on getting results. If it can deliver on the reform agenda of Lisbon and supporting enlargement, bringing countries into the new family of nations proposed at Nice that is the best advertisement for a commission at the heart of the community."