Romantic liaisons between employees at work could soon be brought under tight control, according to the TUC.
Passion in the workplace can take its toll on colleagues
The trades union group has said firms in the UK are planning to introduce "love contracts" to tackle problems when workplace relationships turn sour.
Firms want to copy their counterparts in the US, where staff pledge to behave professionally if they become emotionally entangled, it said.
But such contracts could be in breach of the Human Rights Act, the TUC said.
The contracts are designed to protect companies from the acrimonious fallout that can follow when workplace relationships come to an end.
However, the TUC said controls on the personal behaviour of employees would be inappropriate in the UK.
"It's hardly surprising that relationships do start round the water cooler, after all we work longer hours than anyone else in Europe," said TUC deputy general secretary Frances O'Grady.
"Of course, it is right to be careful and think through all the implications, but heavy handed rules and blanket bans fail to understand human nature and may very well be illegal."
The TUC said employees would have grounds for taking a claim for unfair dismissal if they were sacked for refusing to sign a love contract.
It is estimated that one in four relationships start at work.