The fit notes allow GPs to state that an employee may be fit for a return to work with certain employer support, such as workplace alterations or amended duties.

According to the government, the introduction of fit notes could save the economy £240m over 10 years by helping people on long-term sick leave return to work.

Lord McKenzie, minister for the Department for Work and Pensions, said: "The fit note will reduce the cost employers often have to bear when people are off sick for a long time.

"With the right support in place, employers and doctors can work with employees to help them get back to work sooner."

However, the British Medical Association (BMA) has warned that more needs to be done to help SMEs understand their responsibilities.

Dr Laurence Buckman, chair of the BMA's GPs' committee, told the BBC: "It will be down to the employer to be flexible enough to accommodate [the needs of the worker].

"We think much more needs to be done to ensure employers, in particular local line managers, have enough information about the changes."

Dani Novick, managing director of recruitment company Mercury Search and Selection, added that there was a risk that the new fit notes would be largely ignored due to a lack of understanding.

"There is a risk that everyone from GPs to individuals to employers will simply carry on as they were and ignore the intention here," she said.

"But this is a great opportunity to change the mindset from the assumption that someone will be away from work until they are completely recovered to one where the expectation is that they will get back to work as soon as possible."

Meanwhile, the government has announced that it will extend its occupational health Adviceline pilot scheme to cover every employer with up to 249 employees in Britain.

Further information can be found at www.workingforhealth.gov.uk/Initiatives/OccupationalHealth.