It's never easy following through on an electoral pledge, and if any politician knows how difficult it is, then it must be the French president, Nicolas Sarkozy.

So far he has failed miserably on last year's major presidential campaign promise to increase the purchasing power of the average man and woman on the street here in France and kick-start the sluggish economy he inherited.

But Hallelujah on Monday a minor miracle happened, when his plans to overhaul the French constitution - another key electoral promise - received the parliamentary seal of approval from the country's elected representatives.

Now this is far from being the stuff to whet the appetite of most readers, but bear with it for a moment because there's plenty of substance in what happened in the run up to the vote, and the far-reaching consequences for French politics.

Sarkozy's "victory" was not one easily gained. There had been weeks of arguing, back-room negotiations and comprises as the reform package passed separately through both chambers of parliament, the National Assembly and the Senate.

But for any constitutional changes to be made in France, both had to meet in a joint session in the sumptuous setting of the chateau of Versailles, and a three-fifths majority of votes cast were required for the reforms to be endorsed.

Right up until the last moment the vote was too close to call. The opposition Socialist party had promised to vote "no" and there were even some members of the governing centre-right Union pour un Mouvement Populaire (Union for a Popular Movement, UMP) who were less than happy with the proposed reforms.

In the end though, the bill got the backing of 539 parliamentarians - just one more than the three-fifths necessary - with only one high profile Socialist, Jack Lang, breaking ranks and voting in favour.

Lang's "defection" was perhaps not too much of a surprise as he had served as vice president on the commission charged with proposing many of the reforms. But his decision is likely to have made him even more persona non grata among the Socialist party faithful than he already is.

So what of those reforms - said to amount to the biggest shake-up of the Fifth Republic's constitution since it was first introduced by Charles de Gaulle back in 1958?

Well they include changes to make the president more accountable to a parliament. It'll be able to veto some presidential appointments and the government will be forced to seek parliamentary approval for a military operation (abroad) lasting longer than six months.

The number of terms a president can serve will be limited to two (periods of five years) and the process of allowing national votes or referenda on issues will also be possible if the requisite number of signatures are collected and it has political backing.

So in a very real sense the changes can be, and have been interpreted by many, as at the very least boosting the powers of parliament. Indeed a weekend opinion poll before the crucial vote showed that almost 70 per cent of the French questioned supported the changes.

But while many - and in particular Sarkozy himself of course - are claiming the vote to reflect a "victory for French democracy", critics and in particular the Socialist party claim that the reforms will further weaken the role of the prime minister - already appointed and dismissed at the head of state's discretion.

They fear in particular that the most controversial of the reforms included in the package - allowing the president to make an annual state address directly to parliament along the lines of the US president's state of the nation speech.- will blur the boundaries between the executive and legislative arms of government.

The separation of powers has been an essential part of French politics since 1873 and the president has been banned from appearing in person before the National Assembly or the Senate.

Opponents, and in particular the Socialist party, also claim that the reforms will help create a de facto "monocracy" in which the system of government will be reduced to virtually just one person - the president.

But the stance of the Socialist party itself hasn't been without its own critics even among parts of the media that would ordinarily give the party its backing.

The left-of-centre national daily Lib