Tesco’s application to extend the size of the Streatham Hub superstore by more than 50 per cent was approved last week in controversial circumstances.

Part of Lambeth Council’s planning committee said the application should not have gone ahead because of a “cock-up” in consulting the public over the development.

An error meant Lambeth Council’s website advertised the closing date for comments on the application for October 25, two weeks after the meeting to decide the application.

Councillor Jeremy Clyne also said at the meeting “misleading literature” – including council newspaper Lambeth Life – could also have confused residents on the expiry date.

He told the meeting at Lambeth town hall a number of leading community and business groups were not approached – including Streatham Action, that represents businesses in the area, and leading environmental group, Sustainable Streatham.

A vital consultation document from the Greater London Authority (GLA) was only presented to the committee at the meeting by a councillor, even though the GLA said it was sent to Lambeth Council on October 6.

Officers said they had not received it.

Planning committee member, Councillor Brian Palmer, said the mistakes left the council exposed to an expensive legal challenge should the meeting not be postponed to account for the “muddle”, especially when the council had a close association with the application.

It was a change to the store approved as part of the Streatham Hub development – that includes Streatham’s new leisure centre and ice rink, part funded by the council.

But chairwoman Diana Morris said, after advice from officers, she could think of “no class of person that had not been consulted” and the meeting should go ahead.

Thousands of letters were sent to residents and stakeholders with the correct consultation expiry date on, many community groups and residents had replied, and the error had only been on the website for a week, the meeting was told.

The expansion, increasing the store’s floor space to some 60,000sq ft, was approved after more than four hours of debate.