If his 2015 manifesto is going to feature a load of pledges he can’t stick to, shouldn’t Nick Clegg at least have some fun with it?

If it’s grown-up to ignore what you said to get elected, why have a campaign at all?

A beer pump at the Marquis of Granby public house in Westminster displays a caricature of Liberal Democrat party leader Nick Clegg on April 7, 2010 in London, England. (Getty Images)

The Liberal Democrats have announced promises for the next election, starting with a mansion tax and pensions, but as no one can possibly believe them after last time, they might as well have a laugh, with policies such as the abolition of gravity and replacing buses with pterodactyls.

Nick Clegg could promise that Vince Cable will learn to talk to wasps, that by 2017 everywhere you go will be downhill, criminals will be given gallstones until they learn to be good, and on the soul of his grandmother he pledges that every pensioner will be given a panda, paid for by selling Margate to Brazil.

The problem Clegg has is that once you’ve broken your word so blatantly, you can’t expect to be trusted next time. Serial adulterers face the same dilemma, but at least they usually display some self-awareness. The Lib Dems’ best chance might be to start their next broadcast with Clegg saying: “Listen to me honeypies. I’ve changed. I know I’ve been bad, but I was in a dark place when I trebled them fees, sweethearts. I was confused between trebling and abolishing, you got to believe me, I wouldn’t hurt you, it will be different this time, you know that.”

Then he could announce that, if elected, his party will abolish tuition fees, which is an even more impressive pledge than last time, because this time they’re three times as much, so will take even more abolishing.

Apparently Danny Alexander says his party has worked out the banding of properties for the mansion tax, and a “senior Liberal Democrat” has promised that “we’ll reduce the deficit with a more equal distribution” of something or other, but they’d be better off spending their time learning to play the piccolo or building a canoe.

It’s like a junkie telling you how this time the £200 he wants off you really will be paid back on Thursday. The carefully costed details don’t determine your decision so much as how last week he robbed your kids’ teddies and sold them for £12.

To be fair it doesn’t do the Lib Dems justice to judge them on the famous lie about tuition fees, as they told plenty of other lies as well. For example, during the election campaign they derided the Conservatives for secretly planning to put up VAT, despite saying, “We have absolutely no plans to raise VAT.” This turned out to be entirely accurate, except that the Liberal Democrats joined them in the coalition, and then supported them putting up VAT.

The excuse for this was that in government “we have to be grown up”. Because when you’re grown up you do the opposite of what you promised. Presumably, Clegg tells his wife: “I’ve got good news dear, I spent that night away at the G20 summit with a pair of hookers, so you don’t have to worry about me being childish like those people who keep their wedding promise.”

In any case, if the grown-up way is to ignore everything you said to get elected, why bother having an election campaign at all? For the televised debates at the next election, Clegg might as well bring in a guinea-pig, and when he’s asked about his plans for defence, he can ask David Dimbleby, “Would you like to stroke Oscar?”

The explanation he offers for this behaviour is that his party didn’t win the election, so he had no choice but to compromise. This might make sense, if he’d said, “Although we don’t agree with raising VAT or trebling tuition fees, as part of the coalition we’re forced to go along with it, in return for looking grown-up.”

But when they backed these measures that they’d screamed against a few weeks earlier, they did it with chilling enthusiasm, raging against anyone who objected, with a transformation so sudden and complete that if Clegg was an athlete everyone would have muttered that he must be on steroids.

Several commentators suggested this wouldn’t affect him at the election, as “people will have forgotten about it by then”. I suppose it’s possible some people will forget why they’re 27 grand in debt. They might think, “I’ve got to spend 20 years repaying my loan, and can’t for the life of me remember what I borrowed it for. Maybe I bought a solid gold lawn mower and lost it on the way home. Still, whatever it is there’s no reason not to vote Liberal Democrat again.”

Nick Clegg might protest that he did at least apologise, so instead of a manifesto, he could produce a list of measures he’s planning to apologise for having done the opposite of. But even the apology wasn’t for breaking the promises, it was for making them in the first place. To have any chance at the next election, even of saving his own seat in Sheffield, he’ll need to go much much further than that.

So instead of wasting effort compiling more promises, his one chance of saving his seat in Sheffield might be a collaboration with local heroes the Arctic Monkeys, in which he sings: “Oh what a scummy man, you can see it in my eyes yeah that I’ve got a nasty plan, I’d go into coalition with the bloody Taliban for a place in the cabinet. And you’ve seen me with Osborne and Hague, there ain’t no promise on which I won’t renege, students do better to vote for the plague ‘cos I’m a scumbag don’t you know.”

Twitter: @mrmarksteel