The Guardian has coverage of the Intergenerational Foundation's report arguing that the localism act hands power to older generations.
The report argues that local tiers of government are completely unrepresentative of their voters. This is certainly true, although (as the Guardian piece argues) this is certainly true of other tiers of government and would also hold for other groups (e.g. ethnic minorities).
Whether the lack of representation is a problem depends on whether the decision they make consistently advantage one group over another. The Intergenerational Foundation think this is a particular problem in the area of planning. As the Guardian reports it: "[...] the report cites strong statistical evidence that older people are more likely to be opposed to change, such as new development in a rural area than their younger counterparts: 45% of people aged 55 and above had formally objected to a local planning application to build houses, compared to just 8% of those under 25."
I am sympathetic with the general argument being made here, but I do wonder whether this particular fact provides strong statistical evidence of a bias. Imagine that the arrival rate of planning applications is random and that the probability to object is independent of age. In the 7 years (from when they are aged 18 to 25) 8% of individuals end up objecting to a planning application. That gives a rate of about 1.14% of the age group complaining in any given year. If this cohort lives to be 55, how many of them will have complained at some point in that time period: roughly 43%.
So, whether this is strong statistical evidence on a bias depends on whether the question asked of people specified a time limit or instead just asked if they had ever objected. Unfortunately, the NHPAU report that was the original source doesn't provide details and the archive section of yougov (who did the poll) is a broken link. The situation is also complicated by the fact that the arrival rate of applications may be biased towards home owners.
In short, while the argument fits with my NIMBY prejudice, I am not sure it confirms it.
[Update: Via Jonathan Jones: Looking at the actual report, it seems the Guardian added together "25% of 55–64s & 20% of 65–74s"! p16]
[Update 2: Via Geography Jim: British Social Attitudes better on this (p.68); Although I think you would want to net out location and income before attributing to age (see tables 5.7 and 5.8)]