The European Parliament, once a consultative organ with limited political clout, has increasingly flexed its muscles of late.

The latest challenge to member states’ governments came on Wednesday, when legislators rejected a carefully crafted deal on the European Union’s next seven-year budget.

“You do hear a few officials from the member states, not to mention government ministers, who do consider the European Parliament as a nuisance and question its legitimacy,” said Marco Incerti of the Centre for European Policy Studies, a Brussels-based think tank.

The 754 directly elected EU lawmakers were granted a raft of new powers by the 2009 Lisbon Treaty, including the ability to reject the bloc’s expenditure plans.

“I am struck by the growing role that the parliament is taking among the European institutions, and to ignore it is folly,” French Finance Minister Pierre Moscovici recently told Socialist EU lawmakers.

The parliament recently used this clout to demand a cap on bankers’ bonuses in a package of financial sector reforms - winning over all member states except Britain, which fears the measure could harm London’s appeal as banking hub.

In the last year, it has also: rejected the international copyright deal ACTA; held up negotiations on Europe’s border-free Schengen area; and - in a row over gender representation - opposed a senior European Central Bank appointment.

The EU’s architects saw the parliament - the bloc’s only directly elected body - as a crucial mechanism to balance decisions taken in Brussels, often made behind closed doors.

But the parliament’s strengthened role also adds layers of complexity to the already difficult process of reaching agreement among the EU’s 27 member states.

“I don’t think (EU member states) should allow the parliament to force its hand,” one EU diplomat said recently.

Unlike domestic parliaments, where governments tend to enjoy large majorities and so can count on approval, the European Parliament has its own electoral cycles, which bring different parties to power. That is complicated further by national allegiances.

The 2009 treaty changes have boosted the parliament’s perception of itself, according to Incerti, who said the institution had “come of age” in recent years.

“Even in areas where we already had power, we are more ready to wield it,” said Sharon Bowles, who chairs the parliament’s economic and monetary affairs committee.

In particular, the onset of the financial and economic crisis had prompted EU lawmakers to “feel strongly that they are closer to the voice of the people,” Bowles said.

But the parliament’s critics argue that the citizens of Europe have not yet given it their voice as, even in European elections, they vote with a national mindset - if they bother to vote at all.

Only 43% of Europeans took part in the 2009 elections.

But Bowles warned against getting “all caught up in the issue of democratic legitimisation,” arguing that national governments often had little more than a “veil” of popular representation.

As an example, she cited financial policy in her country, Britain, which was usually proposed by the regulator and adopted by government.

“There is no parliamentary examination,” she said, “How democratic is that?”