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Bullying in the workplace is growing, with many people too afraid to speak up about it, according to the conciliation service, Acas.

Over the last year, Acas said it had received about 20,000 calls about harassment and bullying at work.

Some callers to its helpline had even considered committing suicide.

In a consultation paper, it said businesses need to take the issue much more seriously and to improve anti-bullying policies.

The chair of Acas, Sir Brendan Barber, said bullying was on the rise in the UK.

"Callers to our helpline have experienced some horrific incidents around bullying that have included humiliation, ostracism, verbal and physical abuse," he said.

"But managers sometimes dismiss accusations around bullying as simply personality or management-style clashes, whilst others may recognise the problem but lack the confidence or skills to deal with it."

Zero tolerance

The Acas analysis shows that bullying is more common in certain groups. These include:

public sector ethnic minority workers

women in traditionally male-dominated occupations

workers with disabilities and health problems

lesbian, gay and transgender employees

It said many employers lack the skills to tackle the issue. Often managers just moved staff around, rather than investigating and dealing with the problem behaviour.

The study recommends that workplaces agree on acceptable standards of behaviour, with senior managers acting as role models.

The TUC has said that every organisation should have a zero-tolerance anti-bullying policy.

One expert on bullying agreed that poor managers were often to blame.

"Although bullying takes place at all levels within the workplace, the most common perpetrators are managers," said Shainaz Firfiray, assistant professor of organisation and human resource management at Warwick Business School .

"This type of bullying often arises due to an unequal balance of power, with managers attempting to control the behaviour of their subordinates through coercive methods," she said.