The Socialist group in the European Parliament fears that the centre-right European People's Party (EPP) will obtain twice as many seats in the next Commission.
Such an outcome, they argue, would distort the results of the June 2009 European elections.
Following the election, the EPP obtained 264 MEP seats in the 736-seat parliament, followed by the Socialists with 161 MEPs.
Fourteen EU countries have centre-right governments or have coalitions in which the centre-right is the senior partner, with some having already announced their intention to have a commissioner representing the European People's Party (EPP).
One of those countries - Greece - may change leadership following early elections on 4 October.
At present, the centre-left is in power or is a senior coalition partner in only five EU countries: the UK, Spain, Portugal, Slovakia and Hungary.
In other countries - Romania, Austria and Germany - they are part of "grand coalitions", although in the latter, Chancellor Angela Merkel clearly indicated she would try to oust the Social Democratic Party and replace it with the liberal-affiliated Free Democrats (FDP), following the 27 September national poll.
Denmark, Ireland and Finland have liberal-dominated governments.
In such a situation, the centre-left may fail to achieve its objective of grabbing several important portfolios, as announced by Socialist Group leader Martin Schulz recently.
Speaking on the record, Dimitris Komodromos, press officer of the Socialists and Democrats group, told EurActiv that the goal of his party was to have a Commission "with a social and European direction".
"During the last bureau meeting of the [Socialist and Democrats] group, we decided to call on all Socialist parties and in particular those who are in government, to press Mr. Barroso to give the Socialists important portfolios," he stated. He admitted that his group was aware of the fact that the EPP was dominant in most EU countries' governments.
Schulz recently mentioned industry, environmental policy, international cooperation, development, justice, trade and the internal market as the centre-left's preferred portfolios.
Asked if this was a realistic objective, Komodromos said it was "not impossible".
"Mr. Barroso knows that to have a democratic majority, he needs the support of the Socialist group. Otherwise he will be the president of the EPP and the Eurosceptics. For his legitimacy, he absolutely needs the support of the Socialist group. This is why he adopted a progressive approach in certain things, preparing for meeting our group on Wednesday (9 September)," he said.
However, the plans of the Socialist and Democrats already appear to be in jeopardy, as Romania and Slovakia, which in theory could have sent Socialist commissioners, have indicated plans to propose non-affiliated personalities.
