The Public Health Laboratory Service found a significant link between prescribing patterns of GP surgeries and resistance levels to antibiotics among certain bacteria.

The research is the first to find a direct connection between doctors who prescribe more antibiotics, and the rise of resistant bacteria.

The variations in antibiotic prescribing between GPs were immense - some were giving out nine times more of a common drug than others.

E.coli bacteria, responsible for urinary tract infections, had twice as much resistance in the worst areas as the best, researchers discovered.

Researchers found that some bacteria had more resistance

Antibiotic resistance is well recognised as a significant health problem, which experts fear could lead to medicine offering little or no conventional defence from common infections.

The PHLS in Wales looked at a range of different antibiotics prescribed by 190 GP surgeries serving 1.2 million patients.

It compared the level of antibiotics prescribed on average per surgery, and the level of resistance to antibiotics among the bacteria bothering the local population.

The more antibiotics used by a surgery, the higher the resistance.

However, the authors were quick to point out that there might be valid reasons, such as a predominantly elderly population, why one GP might prescribe far more antibiotics than another.

Dr Tony Howard, Director of PHLS Wales, and a co-author of the study, said: "We're certainly not saying that GPs should not be prescribing antibiotics.

"But our work underlines the problems of increasing antibiotic resistant as a result of community prescribing as well as hospital prescribing.

"The more resistance there is in these organisms, the more difficult it is to treat them."

He said resistant bacteria would mean increased "longevity and severity" of illness.

Resistant bacteria can take longer to eradicate

"It's a reminder that the resistance problem isn't simply a national problem, it may be determined by local prescribing."

The government, aware of the dangers posed by increased resistance, is campaigning to encourage doctors not to give antibiotics unless there is a real need to do so.

Doctors have complained that many patients come to the surgery and demand antibiotics even for illnesses which do not require them.

Dr Jim Kennedy, the prescribing spokesman of the Royal College of GPs, said that the UK in general compared favourably with other countries in terms of antibiotic use.

He said: "Patients are increasingly aware of the pros and cons of antibiotics and supportive of their appropriate use.

"They should remember that their next infection or illness may not require antibiotics for treatment and antibiotics do not work on viral infections."