Richard Porritt believes cracks are beginning to appear within the coalition.

The coalition is creaking.

For the first time since the Liberal Democrats and Conservatives were forced together serious cracks are showing. When quizzed about the partnership, and in a bid to appear grown up, senior members from both sides have always wheeled out their stock answer: “There are differences within these two parties and we are not always going to agree but we are focused on tackling the deficit.”

That may be so and it does appear that the Treasury arm of this political experiment gets on well. But many are shocked it has taken this long for the spats around the edges to start spilling out in to public.

One thing they do agree on – in principle – is reform of the House of Lords. But then everyone appears to agree with that – and everyone seems to have agreed on it for many years.

But unfortunately for Nick Clegg his trophy policy faces a long wait back on the drawing board after the cancellation of the vote to limit the time available to debate the bill.

So, they are all agreed on reform. Excellent. When will it happen? Probably not any time soon.

The Lords debacle shines a light on the state of the coalition and for the all smiles in public, behind the scenes it is getting more fraught. The Government pulled the vote on the Lords which would have pushed legislation through because Number 10 feared it would lose. The anger among Tory backbenchers had grown to such a level that Mr Cameron took his bat and ball home.

Number 10 would claim the bill was a success of course – but neither the Lib Dems nor the almost 100 Tory MPs who voted against it would agree with that. If it does get a firm boot into the long grass you can bet Mr Clegg will continue to remind Mr Cameron of the coalition agreement and the potentially destructive power he wields.

Bernard Jenkin was one of the most senior Tories to campaign against the bill. He told East meets Westminster: “This retreat represents a defeat for this bill. The Government would be wise to withdraw it and concentrate on jobs and growth, rather than trying to fix a part of our constitution which works very well. If they persist with this bill the political crisis may well shorten the life of this coalition and bring forward the date of the next general election.”

Music to Labour leader Ed Miliband’s ears but if, as Downing Street sources suggest, a new time motion is tabled at some point in the future to stop the bill being talked into the abyss he faces a tough decision after instructing his MPs to back the principle of Lords reform but not the super-quick schedule. Will he be able to resist his chance to inflict yet more damage on the coalition?

The Prime Minister is certainly rattled by his own MPs defiance of the whips. In tense scenes outside the division lobbies he even confronted one rebel – Jesse Norman – and the feeling is that the mood within the party is soured. Add to this the lingering threat of the Liberal Democrats sabotaging the boundary review – which would significantly help Tory chances at future elections – and Mr Cameron faces tricky times.

“A deal is a deal,” Lib Dem deputy leader Simon Hughes said yesterday – but it appears many Tory MPs do not see it that way.

So Mr Cameron faces a dilemma. He is – he hopes – a little under three years from a General Election but if that is to be the case he needs the Lib Dems to stick with him. If they turn their backs on the Tories now Mr Cameron faces going to the nation early – and with the economy still in the doldrums.

The Tories have pinned their hopes of success on sorting out the economy. They want to be able to say to Britain: We have saved the economy, vote for us. Only problem is they have not managed this yet.

Equally, though, the last thing he needs is growing unrest within his party, many of whom think the junior coalition partner has far too much power.

The current political climate is unprecedented and faces calling into question the collective responsibility of the cabinet.

The only example of a British coalition since the wartime national government was the Lib-Lab pact in 1977.

Back then the agreement meant an increasingly powerful Margaret Thatcher was unable to force a vote of no confidence on Jim Callaghan’s Labour government. But this was a long way from the coalition Britain has now.

The Liberals – as they were back then – were lured with the opportunity to influence but, their heads dizzy with the prospect, they apparently forgot to demand anything in return for their loyalty to the government. Labour did offer a joining consultative committee to examine Government policy but it meant nothing.

At the time Mrs Thatcher remarked that she was “astonished” the Liberals had signed up to such a bad deal.

In the end it only meant that Mr Callaghan could cling to power for a little longer. In the autumn of the following year the pact was dissolved amid a belief an election was to be called.

In reality Labour stumbled on until the spring when the Tories and Mrs Thatcher swept in to Number 10.

It is a stark warning from the past for Mr Cameron: Take hold of your party and your coalition partners if you want to stay in power.

Richard Porritt is on Twitter @Porritt.