The BBC's Sue Nelson: "2000 scientists use the Daresbury research facility"

Two rival locations are in the running but workers at the north of England site are warning that at least 550 jobs will be lost if the government chooses the site in Oxfordshire.

The facility, called a synchrotron radiation source, is shaped like a giant hoop and generates a high-energy X-ray beam. This can probe the structure of proteins and electronic devices, helping to design better drugs.

The new facility, called Diamond, had been expected to replace the existing one at Daresbury, Cheshire. This was the first to be built in the UK 20 years ago. More than 2,000 scientists across the UK use Daresbury and are keen to see the bigger, better machine built.

Surprise rival

But earlier this year a rival emerged - the Rutherford Appleton Laboratory (RAL), in Oxfordshire.

"What surprised me was the sudden emergence of a preferred location in the south of England without, in my view, there being a full and open debate of the characteristics of all the sites involved," said machine designer Vic Suller.

The BBC's Sue Nelson: "If the site goes elsewhere, it will have dramatic consequences for the economy"

If the government decides against Daresbury, hundreds of jobs - and the facility itself - will be at risk, unions have warned.

Transport and General Workers' Union spokesman Vinnie Goulding said the loss of the facility would have dramatic consequences for the local economy.

"On this site alone it would mean the loss of 550 jobs within three to five years. We'd start winding down almost immediately. There's no other science up here," he said.

'Wellcome' funding

However, the �110m of the cost of the synchrotron will be met by the Wellcome Trust, which is based in the south east near the RAL.

The French Government is also contributing money so that its scientists can access the machine.

Robert Jackson is the MP in whose constituency the RAL lies and is also a former science minister. He believes the site should be based in the south east.

"Accessibility, proximity to other machines and the existence of a strong managerial capacity are all important considerations," he said.

"And all of those would argue in favour of the RAL."

Government leaks suggest that the RAL is the favoured choice. But none of the main players will discuss the matter until the decision is made by Trade and Industry Secretary Stephen Byers.