It's one of the cardinal rules of politics - be careful what you're photographed with. At the weekend, Ed Miliband broke it spectacularly.

Days before the UK general election, the Labour leader posed before a giant stone slab inscribed with six of the party's key policies.

"These six pledges are now carved in stone, and they are carved in stone because they won't be abandoned after the general election," Mr Miliband said.

In the UK, as in the Antipodes, public consternation has swelled around a perception that politicians can't be trusted to keep their promises. Labour's stunt - including an undertaking to erect the monument at 10 Downing Street if the party formed government - was intended to counter that concern.

But the move quickly backfired. Observers noted the tablet's striking resemblance to a cemetery headstone - with Iain Macwhirter, political commentator at Scotland's Herald newspaper, declaring it the worst photo in general election history. "Ed Miliband unveils his tombstone even before he's been buried," he wrote.

Would that that were the extent of the gaffe. But in the age of Photoshop, the only thing more open to mockery than a politician posing with a tombstone is a politician posing with a tombstone that has writing engraved on it. Mischief-makers in the UK and Australia welcomed the invitation.

pic.twitter.com/csHfBnircc— Rupert H (@rpy) May 3, 2015

pic.twitter.com/UxGIO5GXfH— Tom Phillips (@flashboy) May 3, 2015

Although Labour is competitive in national polls, it is far from commanding a majority, and the expected election outcome is a hung parliament. The embattled Mr Miliband has been relentlessly targeted by conservative newspapers that have branded him as "Red Ed" and "Calamity Ed".

The weekend's unfortunate stunt has only added fuel to that fire. The tombstone has been dubbed an "EdStone", a "policy cenotaph" and "the heaviest suicide note in history" - a reference to former UK Labour MP Gerald Kaufman's rebuke of his party's 1983 election manifesto, which he called "the longest suicide note in history".

British PM David Cameron said the stone was demonstrative of Mr Miliband's lack of political nous. "If you have got a problem with judgement, I don't think that's going to help," he said.

'the heaviest suicide note in history' #EdStone— Chris Deerin (@chrisdeerin) May 3, 2015

I'm certain that @UKLabour's #EdStone is a deleted scene from The Thick of It.— Martin Poile (@MartinPoile) May 3, 2015

Don't let @Ed_Miliband & SNP carve the tombstone to Britain's economic recovery. #VoteConservative on 7 May #EdStone pic.twitter.com/hAf6kCZmIM— CCHQ Press Office (@CCHQPress) May 3, 2015

While the Conservative London mayor, Boris Johnston, tweeted that the stunt was "a waste of good stone".

"I think it is absolutely crazy that you've already got the Labour leader commissioning great stones that are going to be engraved like the commandments of Moses or Hammurabi with what he wants to do," he told the BBC.

Despite conjecture that the tombstone would further weaken Labour's declining fortunes at the May 7 election, Mr Miliband is not the first British political leader to be photographed in a compromising position and survive - or even thrive. This picture of Mr Cameron was snapped during a previous campaign in the Scottish town of Dunfermline by photographer Michael Schofield.