Hardly the sexiest headline by any stretch of the imagination. But there again when it comes to institutional reform and changes to the constitution, the subject matter is hardly guaranteed to instill much enthusiasm.

The French president, Nicolas Sarkozy is fighting constitutional reform on two fronts. There is of course the debate over how to deal with the Irish “no” vote in June to the Lisbon treaty. He’ll be tackling further that issue on July 21 when he pitches up in Dublin in his role as the EU big cheese while France holds the 27-nation bloc’s six-month rotating presidency.

And this week will see his attempts to update the French constitution receive either final parliamentary approval or a political slap in the face.

The vote is too close to call with some likely splits in the governing Union pour un Mouvement Populaire (Union for a Popular Movement, UMP) party and the opposition Socialist party promising to reject the changes.

The reforms themselves have already been passed separately by both chambers of parliament, the National Assembly and the Senate. But for constitutional changes to be made, both have to meet jointly and vote together at a special session opening in Versailles on Monday. A three-fifths majority of votes cast will be needed for the reforms to be endorsed.

At stake basically is one of Sarkozy’s electoral promises to change the way politics works here in France.

Among the proposals are moves to make the president more accountable to parliament, allowing him (or her) to appear directly before both chambers. Another clause would require the government to seek parliamentary approval for a military operation (abroad) longer than six months. The number of terms a president could serve would also be limited to two (periods of five years) and the process of allowing national votes or referenda on issues would also be possible if the requisite number of signatures were collected and had political backing.

So in a very real sense the changes could be interpreted as at the very least boosting the powers of parliament.

So what exactly are the fears of the opposition to a reform which on the whole has also received fairly widespread popular support in France – if the most recent opinion polls are to be believed?

Basically the main opposition party, the Socialists, fear that allowing the president to address parliament directly will blur the boundaries between the executive and legislative arms of government.

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

In trying to reach a compromise, Sarkozy has suggested an annual state address to parliament along the lines of the US president’s state of the nation speech. But even that has met with only lukewarm enthusiasm.

In the past couple of weeks Sarkozy has also made more concessions – proposing for example that opposition parties have equal (television) airtime to address issues raised by the president whenever he appears on the small screen over the course of a year.

But the Socialist party in particular has held firm in maintaining that it will present a united front in Versailles and vote “no”.

While it might be hard to figure out exactly why the Socialist party isn’t supporting the reform – apart perhaps from refusing to accept a centre-right inspired proposal – it must appear even more difficult to understand why some members of the governing UMP party might break ranks.

There again as the reforms have passed through parliament to the final vote, a number of compromises have been struck which leaves the reform package, as far as some of them are concerned, almost a shadow of what was first put forward.

To get the majority needed, the government is counting on – and indeed will need – some defections from the Left, and one such vote could come in the shape of a high profile former Socialist minister, Jack Lang, who has apparently still not made up his mind how he will vote.

Lang calls the changes modest and far from the wide-ranging proposals envisaged by a parliamentary committee of which he is a member, to look at the overall reform of France’s institutions.

Even though the Socialists are calling for a united front in voting “no” in Versailles, which would certainly stop the changes to the constitution being made, there are also some waverers, and they could just tip the balance.

Critics of the Socialist party’s stance have claimed that their opposition to the reforms is based more on principle than conviction and a simple look at the latest opinion polls would tell them that a healthy majority of French voters are in favour of the reforms.

In a weekend survey, almost 70 per cent of those asked said they supported the changes.