Nearly half of UK companies want doctors trained to improve their advice on activities workers can perform, the survey showed.
Responding to reports that GPs' poor handwriting had left some fit notes illegible, officials at the Department of Work and Pensions said this was 'not a huge problem'.
Only a small percentage of Med 3s submitted since April had been illegible, a spokesman said.
Uncertainties over NHS IT have made it unclear if electronic Med 3s will come into force this year.