London Councils Race to Fix Duplicate Image Crisis in Planning Portals This Week

Planning applications across at least six London boroughs have been stalled this week after a technical fault in the Idox Uniform planning portal — used by more than two dozen councils in England — began generating duplicate image attachments on submitted documents. Officers at Southwark, Hackney, and Tower Hamlets confirmed the problem is causing manual review delays, with some files running to three or four times their expected size because the same site photographs are being appended repeatedly to each submission.

The timing is poor. The Starmer government has staked significant political capital on speeding up planning decisions as part of its housing reform agenda, with the Planning and Infrastructure Bill working its way through Parliament. Any slowdown in borough-level processing undercuts that push directly. The Greater London Authority's own development pipeline — which includes schemes along the Thames at Silvertown and Thamesmead — depends on timely local decisions feeding upward into the strategic planning process overseen by City Hall.

What Went Wrong — and When

The fault appears to have surfaced around 30 June, when a software update pushed to Idox-connected portals altered the way image metadata is cached during PDF compilation. Instead of embedding a photograph once, the system began re-embedding it at each internal document reference point. A single application for a three-storey extension in Bermondsey that would normally generate a 4MB PDF was reportedly submitted as a 47MB file, according to planning officers familiar with the issue who declined to be named because they were not authorised to speak publicly.

Borough planning teams began flagging the problem to Idox — the Glasgow-based software company that supplies the portal — early this week. As of Friday morning, a fix had not been publicly confirmed. The Local Government Association, which represents English councils, has been in contact with affected authorities but had not yet issued formal guidance as of the time of writing.

Hackney Council's planning department, based on Mare Street in east London, has been advising applicants since Wednesday to resubmit compressed image files and to contact the duty planning officer before lodging new applications. Tower Hamlets, where the pipeline of applications linked to the Whitechapel and Poplar regeneration corridors is substantial, has posted a notice on its planning portal acknowledging delays.

The Practical Impact on Applicants

For homeowners and small developers, the disruption is measurable in money as well as time. A standard householder planning application in London costs £258 in statutory fees as of April 2025 rates — and that fee is non-refundable if a submission is validated as incomplete or returned due to a technical defect. Architects and planning consultants say some clients are now being advised to hold off submitting until the portal issue is resolved, pushing their project timelines back by at least two to three weeks.

Larger commercial applicants face bigger stakes. Several pre-application inquiries tied to schemes in the Old Street roundabout area and along the Lee Valley corridor were due to progress to formal submission this week. At least two firms, speaking anonymously because of ongoing negotiations, said they had pulled back their submission dates until the system is stable.

The issue also lands awkwardly for Sadiq Khan's office, which has been pushing borough councils to improve decision speeds under the London Plan's performance framework. Boroughs that miss the government's target of deciding 70 per cent of major applications within 13 weeks can face intervention from the Planning Inspectorate.

Applicants with pending submissions are being advised to download and manually check every PDF before lodging, keeping image files below 1MB each where possible and using JPEG rather than PNG format. Anyone whose application was validated between 28 June and 4 July should contact their borough's planning department directly to confirm the file was received without duplication errors. Idox has a customer support line for councils but does not deal directly with members of the public — meaning the burden of troubleshooting falls, as usual, on already-stretched borough officers.