Former Conservative defence secretary Liam Fox once said the Conservative and Liberal Democrat parties, who are now four years into their coalition, are like a couple staying together "only for the kids".

The question, if the analogy can be laboured, is not whether they will split, but how; will the crockery be smashed, or will the one-time partners be still talking or only through their lawyers.

For some, the coalition has already run out of steam. MPs left the House of Commons on Wednesday night for another three-week break, simply because there was not enough legislation to keep them usefully occupied.

“I have never known a parliament as empty of activity as this one. It does feel a little bit like it is the undead running around at the moment,” says Labour shadow Commons leader Angela Eagle. MPs are being accused of being part of a “zombie parliament”, even though they sat for 161 days over the last year – significantly longer than the Dáil, it must be said, which managed to sit for 123 days in 2012 and 2013.

Following the 2010 election, the coalition passed the Fixed-Term Parliaments Act, which stipulates that the next election should take place on May 15th next year and every five years thereafter.

In 1911, Liberal prime minister Herbert Asquith changed the duration a parliament could legally sit from seven to five years; but, in practice, Asquith believed that governments would run out of steam in four.

Average length
So it has broadly proved. Eighteen elections have been held since the end of the war, with the average length of time between elections running at three years and 10 months. Just three parliaments have nudged the five-year limit. Understandably, the Tories and Lib Dems are increasingly feeling the need to stress their own identity as they prepare for Election 2015, making it more difficult to agree on legislation to put before the Commons. Yesterday, Liberal Democrats deputy prime minister Nick Clegg insisted a list of planned Bills be published in early June and would amply fill diaries for the last 12 months – but few in the Commons take that seriously.

However, if legislation is slight, MPs have had a better run in parliamentary committees. These have come to dominate the public agenda during this parliament in ways that would have been unthinkable a few years ago.

Before 2010, the awarding of places on Commons select committees was part of the patronage enjoyed by party leaders, while the majority so appointed then elected the chairman their party leader wanted.

Prized places
Today, the chairs are elected by all MPs, and the places are highly prized. This week, Rory Stewart, who was put in charge of two Iraqi provinces after the 2003 invasion, won the race to be the chair of the defence select committee.

Stewart’s election is significant. Firstly, Conservative MPs elected along with him in 2010 are becoming an increasingly influential, impatient and clearly identifiable grouping within the Tory party. Secondly, it shows that ambitious politicians – and Stewart is very ambitious – believe political power can come through committees, if only because a ministerial seal has not come their way.

Between 1997 and 2010 select committees produced about 1,500 inquiry reports, or 110 a year, along with 40,000 recommendations.

Committees have sometimes humbled the powerful: notably the public accounts committee when tackling the “as little tax as possible” practices of Google, Starbucks and Amazon.

However, much remains to be done. Three years ago, the constitution unit in University College, London, published a detailed examination of the committees’ performance. They were, it said, at their “most influential when they are strategic, timely or persistent”, but they could do more to follow up on past inquiries, rather than endlessly searching for new fields.

MPs, the academics warn, can become blinded by TV cameras when their work hits a nerve. “Public embarrassment is a key form of influence, but committees can sometimes veer towards ‘ambulance chasing’.”