Redevelopment of the Brighton Centre will not start for at least another three years – and it could be longer still.

Sources at Brighton and Hove City Council have revealed lucrative conference events are already being booked for the key venue in both autumn 2012 and 2013, quashing hopes work would be underway by then.

It is now thought the long-awaited revamp will not begin until as late as 2015, contrary to previous reports of a 2012 start.

The bookings appears to confirm rumours in the city's business community that the £400million redevelopment scheme, which also involves the Churchill Square car parks and the neighbouring Kingswest cinema and nightclub complex owned by Standard Life Investments, has lost momentum.

The revamp is widely considered as an urgent priority for the long-term prosperity of the city and the appearance of its seafront.

The council, which owns the centre, insists the project is still on track and said it should have more details next month.

In July it commissioned Make Architects, whose partners have been involved with London's Gherkin and Wembley Stadium, to draw up plans.

A council spokesman said: "Progress with such complex projects will never be rapid and nobody ever said it would be.

"We’re still working on it behind the scenes. But there’s nothing to announce and we hadn’t expected there would be at this stage. We’re hoping to have a clearer idea on timetable in March.”

The ongoing delays will be a disappointment to the hundreds of hotels, bars, restaurants and shops which rely on the business generated by conference delegates.