Age rather than sex or race is the most common form of discrimination in the workplace.

One in five of those questioned in a Mori poll, released to coincide with the start of Age Positive Week, said they had experienced some form of discrimination at work, with 38 per cent citing ageism as the cause.

The research also looked at the public's attitude towards older colleagues, with 34 per cent saying resistance to change was a characteristic they associated with mature workers and 29 per cent saying they felt older workers lacked technological skills.

Of those who said they felt they had been discriminated against because of their age, 38 per cent said this happened at the recruitment stage.

Others said it concerned promotion, the selection stage and training and development.

Age discrimination in recruitment was far more common in men, with 45 per cent citing it compared to 27 per cent of women.

As well as looking at general attitudes to mature workers, those aged 50 to 65, the research looked into the characteristics associated with younger staff aged 16 to 25.

The most commonly cited characteristic was inexperience.

Others included a belief younger workers were unreliable, irresponsible, more likely to take time off sick, lacking organisational skills and liable to stay in their job for a shorter period of time.

Work and Pensions Secretary Andrew Smith condemned age discrimination at work and called for employers to put an end to it.

He said: "Age discrimination in the workforce does not pay. All evidence shows an age-diverse workforce is more productive and efficient with age-positive employers enjoying lower staff turnover rates, lower absenteeism and workers with higher levels of motivation. I won't be happy until age discrimination is a thing of the past."

Pensions minister Ian McCartney said the approach of the campaign could be summed up in one sentence: "Don't let a birth certificate become a P45.

"At a time when the country is experiencing skills shortages in many sectors, whole swathes of the working population are being overlooked solely on the basis of their birth date."

More information is available at www.agepositive.gov.uk.