Workers in a call centre were told that whoever went to the toilet the most would have to wear a disposable nappy.
A manager took a packet of disposable nappies into work and made staff sign a "toilet book" to check how long they were spending in the loo.
He warned that workers who spent the most time in the toilet would be forced to wear one of the nappies.
The incident was revealed by a woman who called a special hotline set up by the TUC as part of a campaign to improve working conditions in call centres.
Almost 400 people called the hotline last week complaining about bullying, long working hours and having to achieve "impossible" sales targets. Other complaints included:
l Being forced to go into work to report sick rather than phoning;
l Having to put your hand up for permission to go to the toilet;
l Only being allowed three seconds in between answering calls.
One caller told the TUC he was disciplined for leaving a six second gap between calls.
Another said her bosses wouldn't allow Christmas decorations because they were a health and safety hazard.
TUC general secretary John Monks said many call centres were making a real effort to improve working conditions and throw off the industry's "sweatshop" tag.
But he added: "These figures show there are still too many centres using bullying tactics to pressurise and intimidate employees."
The TUC will be investigating some of the complaints which it said suggested that some call centres were "openly flouting the law."
Most of the calls were from South Wales (15 per cent), Scotland (14 per cent) and the South-East (12 per cent).
There are over 400,000 people employed at call centres, which deal with customer inquiries for firms.
The TUC hotline, 0800 032 0033, will run until Friday
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article