TRAFFIC in the heart of Brighton will be jammed for six weeks after workmen accidentally poured tonnes of concrete into a sewer.

One lane of Queens Road has been blocked off while workmen replace the Victorian pipe.

Meanwhile, Southern Water is having to pump out the blocked pipe every night into tankers to prevent wastewater backing up into shops and businesses in Queens Road.

The problem was caused when workmen on the controversial North Street Quadrant development discovered a pit which they decided to fill with 30 tonnes of foam concrete.

Unknown to them, they had broken the nearby sewer and, overnight, the concrete flowed in.

They returned to work the next day to find the pit empty. The concrete solidified and filled 10 metres of the pipe. Southern Water engineers crawled through it and hammered out eight tonnes of concrete using hand tools and drills.

But they finally decided there was no alternative but to dig out the blocked stretch and replace it.

Bob Lennard, the firm's principal engineer, said: "We gave it our best but the pipe needs to come out."

He said they were prepared to work 24 hours a day to get the work done quickly to avoid as much disruption as possible but with people living in flats above businesses in the area, it was decided to work only daylight hours.

The problem has been complicated by news the construction company has gone into liquidation.

Developers Wildmoor, based in Chelsea, are understood to be close to hiring a replacement firm to complete the project.

Building control manager Andrew Wilkinson, who acts as an independent building inspector for the scheme, said the problems would probably push the completion date back to next spring.

Work on the site stopped three weeks ago but, Mr Wilkinson said, should restart later this month.

The project is opposite the Clock Tower and comprises shops and flats. The scheme was approved by Brighton and Hove City Council late last year after months of wrangling.

Councillors originally rejected the designs as too ugly.

Southern Water apologised for the disruption. Karl Taylor, regional sewerage manager, said: "This was caused by factors beyond our control."