Even by its own low standards, this year's G8 summit has reached a new low for its cynicism. It is not just that the solemn pledges made at Gleneagles on aid have been broken, it is that the world's richest nations are seeking to hide their own failure.

They are doing so in two ways. First, by removing any mention of Gleneagles from their summit communiqué. Second, by making new promises of financial assistance that – on past form – will either not be fulfilled or only met by diverting money from other parts of the development assistance budget.

Let's be clear about what's going on. Back in 2005, when the G8 last met in the UK, Tony Blair (with the help of Gordon Brown) forced the summit to pledge some serious amounts of cash for development. It was the high point of the Make Poverty History movement and the G8 leaders were shamed into action.

No sooner had the summit ended than the attempts at backsliding on the commitments began. Not by all countries, but by some of them. France, Italy and Germany were the main culprits. Britain stuck to its promises, as did George Bush's United States.

Each year, there would be an attempt to remove the word "Gleneagles" from the communiqué. Each year it was resisted, but only because Blair and Brown put in the time and effort needed to keep the G8's feet to the fire. This required the expenditure of considerable amounts of political capital, but it paid off.

This year, the G8 aid slackers look to have won the day. Unless there is a last-minute push from David Cameron, the language in the communiqué will be bland and meaningless, giving those with budgetary problems ample wriggle room to defer meeting their promises until long into the future.

Will the prime minister force the issue? The signs today were not good. Downing Street was downplaying the importance of the summit language, even though the UK sherpa – the top official who drafts the communiqué – spends hours arguing over a single word or clause that Britain doesn't like.

The detoxification of the Conservative brand required Cameron to match Labour's commitment to raise aid spending to 0.7% of GDP by 2013, but the prime minister's apparent unwillingness to bang the table at the G8 suggests that the commitment to development is just skin-deep.

Every country that hosts the G8 likes to have a big announcement to make on development, to show how big-hearted it is. This year, Canada is focusing on maternal health, a worthy cause to be sure. But the fact that less than half the extra $25bn pledged to Africa at Glenagles has actually been delivered means that the smallprint of any deal should be very carefully scrutinised.

This year, as in the past, the G8 will only be able to come up with a juicy-sounding number by extrapolating past aid trends well into the future and by raiding spending on other parts of the aid budget. The real impact on the ground will be close to the square root of naff all.