The TCPA 1990 provides that the local planning authority must have regard to "material considerations" when deciding on a planning application. The question of what will constitute a "material" consideration was dealt with recently by the Court of Appeal in the case R (Watson) v Richmond Upon Thames LBC & Solum Regeneration Ltd  EWCA Civ 513.
The grant of planning permission for the redevelopment of Twickenham Railway Station was challenged on the basis that the planning committee had failed to consider a report containing objections to the scheme. The report had been submitted by the Twickenham Advisory Panel (TAP), a body set up to advise the council on development.
Lord Justice Richards applied the test set out in Bolton Metropolitan Borough Council v Secretary of State for the Environment which asks whether there was a “real possibility” that a different decision would have been reached had the consideration been taken into account. LJ Richards held that this test was equivalent (for the purposes of the facts at hand) to the test in R (Kides) v South Cambridgeshire District Council, which was to ask whether the consideration would have tipped the balance of the decision-maker's scales to any extent. Although "deeply unimpressed" by the way the council handled the TAP report and surprised that it had not been taken into consideration, LJ Richards found that the TAP report contained nothing that would have altered the committee's decision. The statutory duty to have regard to a material consideration had therefore not been breached. However, what is not clear from LJ Richards' judgement is how a planning committee can know whether something will 'tip the balance' of their decision unless they actually consider it, and you would expect such consideration would need to be minuted.
I also recently considered the case of Derbyshire Dales DC & Peak District National Park v SoS CLG and Carsington Wind Energy. In this case, a distinction was drawn between potentially relevant considerations and necessarily relevant considerations: the decision-maker will not err in law by taking account of the former but will err in law if he fails to take account of the latter. A consideration will only be 'necessarily' relevant if statute expressly or impliedly requires it to be taken into account. This suggests that if an issue is not necessarily relevant, a decision-maker has a choice, within the bounds of reasonableness, as to whether he has regard to it. Again, there remains a lack of clarity here as to which issues statute 'impliedly' requires to be taken into account. Readers' thoughts are welcome!