The Tories and Labour are both clearly on a mission. Their rival manifestoes look uncomfortably, or comically, all too much like religious documents for the comfort of Britain's largely agnostic electorate.

The Tories' starchy blue "Invitation to Join the Government of Britain" reminds me of a book of trusty, well-established hymns. One can easily imagine I Vow to Thee my Country alongside Blake's Jerusalem, which both parties have adopted for their own faux-mystical ends even though the dissident poet would have hated this double misunderstanding of his plea for a world free for untrammelled spirits.

And, yet, if the Tory manifesto is more or less par for the course, although a bit too leftish in its message for the old party faithful (who wants riff-raff joining in the governance of these "sceptr'd isles"?), the Labour manifesto is decidedly, even feverishly and messianically so. From one perspective, this cover calls to mind illustrations found in The Watchtower, the Jehovah Witness house journal, in which perfect 1950s-style families picnic in Elysium fields surrounded by lions and lambs happily lying down with one another.

It's hard, though, not to get the feeling that both parties are sending themselves up. Labour's image of a heroic Soviet-style family, circa 1950, seems to be an in-house joke by someone who enjoys Private Eye's lampoon of Gordon Brown as the Supreme Leader of a half-cock, Soviet-style state. The cover of the Labour manifesto looks for all the world like a kind of run-of-the-socialist-mill poster, promising loyal workers, fecund farms, all-year sunshine and cities that appear like New Jerusalems over far hills crowned with a nationalised halo.

Manifestos tend to be deeply boring, if unintentionally comic, documents, especially this year when the parties have converged more than they are willing to admit to the electorate. The plain blue wrapper of the Tory manifesto might look very different at first glance from its colourful Soviet-chic Labour counterpart, yet at heart these are two parish magazines, or songs of praise, trying – a little too hard – to persuade us of the righteousness of two unholy political parties. In brief, both are very funny indeed, and even funnier taken as a pair.