Launching a fact-finding exercise on the problem, the Information Commissioner's Office (ICO) said nearly a third of young people had received unwanted contact after sharing their details with a business.
"People have the right to order a pizza, or give their email for a receipt, or have shopping delivered, without then being asked for sex or a date a little while later," said Emily Keaney, Deputy Commissioner for Regulatory Policy at the ICO.
The ICO said it would ask major customer-facing employers about the safeguards they have in place against the problem and emphasise their legal responsibilities.
The regulator was contacting the companies due to the high likelihood their staff had come into contact with members of the public, and said it would not prejudge data protection practices while the fact-finding exercise was ongoing.
The actions available to the ICO for breaches of privacy and data protection laws include criminal prosecution and non-criminal enforcement measures.
The ICO is also launching a call for evidence over the extent of the the issue, as the regulator said 29% of 18-34 year olds had been contacted after giving their details to a business according to polling by Savanta.
Keaney said a "disturbingly high" number of people had been impacted and companies could have no excuses if their employees had misused personal information.
"There may be, amongst some, an outdated notion that to use someone's personal details given to you in a business context to ask them out is romantic or charming," she said.
"Put quite simply, it is not - it is against the law."
(Reporting by Alistair Smout; editing by William James)
