Angry building workers are planning a mass demonstration outside the £200 million redevelopment of Birmingham's former BBC headquarters at Pebble Mill in protest at use of 'umbrella' labour on the site.

Construction union UCATT will be demonstrating at Edgbaston today amid claims that workers are being forced to work via so-called umbrella companies, costing them up to £100 a week.

The union says tens of thousands of construction workers across the UK face substantial pay cuts after the Government introduced new legislation in April this year requiring employees to be paid via PAYE.

The new regime means additional costs are met by workers who have to pay both employee and employer National Insurance contributions.

The Pebble Mill development, which will include a new dental hospital and school of dentistry, is being built by Galliford Try and is heavily reliant on umbrella company labour, according to UCATT.

The union says workers, which started on site last year, are also officially paid the national minimum wage, despite having negotiated a rate far in excess of the figure, with pay partially boosted through expenses, performance-related sums and other methods.

But UCATT says holiday pay is rolled up into the rate, meaning that, when workers take annual leave, they are unpaid while payslips are made so complex that workers say they do not understand how their rate is calculated.

Shaun Lee, acting regional secretary of UCATT Midlands, said: "Workers are being ripped off by the umbrella company con trick and they are now struggling to make ends meet.

"It is disgraceful how employers can get away with exploiting construction workers in this way.

"Workers are given no choice, either they work via an umbrella company, or they don't work at all. The Government must step in and crackdown on this exploitation."

Three-quarters of the 27-acre Pebble Mill scheme has already been secured with development partners, including the new dental hospital and school of dentistry set to open next year.