A planning inquiry begins today into proposals to make a huge expansion of The Mall at Cribbs Causeway.
The plan has been slammed by smaller retailers who believe it will affect trade.
But South Gloucestershire wants to see the major development go ahead.
It could see a new wing built, in a development which would include dozens of new shops and restaurants.
The Mall currently has two anchor stores – Marks and Spencer and John Lewis – at either end, and the expansion will see a new anchor store added.
It will increase the space for shops by nearly half again.
It would also provide the centre with a hotel, a multi-storey car park and events plaza.
A public inquiry, being held in Eastwood Park, Wotton-under-Edge, is expected to last for 12 days.
The 35,000 square metre extension was given the go-ahead in November after South Gloucestershire councillors were convinced by The Mall’s promise to create 3,000 jobs through its £300 million investment.
Peter Cooper, the director of the Bristol Alliance, which runs Cabot Circus, said it could lose £123 million of trade and 1,500 jobs over five years if the proposals came to fruition.
The money also came with guarantees to invest in transport infrastructure, which will see a new bus station created for local and MetroBus services.
But the plan was called in by John Penrose, Conservative MP for Weston-super-Mare , stating it could damage Weston’s regeneration and make its “rebirth harder to achieve”.
According to retail assessments, it is predicted that 8.3 per cent of trade, worth £39 million, would be diverted away from Weston by 2021 if the mall was allowed to grow. The decline in profits could lead to one in 12 shops closing, said the MP.
He has called on the Government, which is currently reviewing the planning application, to overrule the council’s decision for the good of the North Somerset seaside town’s tourism and retail industry.
When the inquiry was announced, a spokesman for South Gloucestershire Council, who approved the proposals said: “While we are extremely disappointed, we remain optimistic that the £300m investment which would create 3,000 jobs and generate economic prosperity across the region could still go ahead.”