PhonepayPlus is the UK's regulator of premium rate services including some apps, voting on TV talent shows, directory inquiries and more.
It told BBC Radio 4's You and Yours that there were "problems" with some subscription services.
It is working on proposals to tighten the rules.
You and Yours has heard from listeners who said they had been signed up for these services without their knowledge.
One of those - Jim - found out his 12-year-old son was receiving premium rate texts which contained adult content, at a total cost of more than Â£340. The texts were sent weekly, and each one cost a couple of pounds.
"In August 2015, my son who was aged 12 at the time, was sent a random text from a company, and he was inquisitive and he clicked on the link, didn't know what it was, and by clicking on this link, he subscribed to an adult content site, which were then going to send him four texts every month for the foreseeable future," said Jim.
"Unfortunately, I only found this out a year later when I went to renew his contract at Vodafone.
"I was absolutely appalled as a dad and shocked that this could happen. I should have checked my bills, but it was cleverly done. The way these companies had sent these text messages was like a drip-feed into the account, so there was no sudden spike and I had not picked it up."
Jim said he was appalled at the lack of regulation in the industry.
Simon Towler, director of policy and external relations at PhonepayPlus, said strict rules were in place for the way these services should be operating.
"In the particular case of adult services, in addition to our code of practice, we have special conditions and they should not be sent to 12-year-olds," he said in response to Jim's case.
"A phone is a dumb piece of technology. The service provider does not know that the person at the end of it is a 12-year-old.
"There is age verification when people sign up for a contract, so in this particular instance, it is very likely, particularly with a 12-year-old, that the person who was down as the bill payer, the person owning the phone, was in fact over 18."
Jim was paying the bill, but the phone was registered in his son's name.
A spokesman for Vodafone said: "We are sorry that the customer has had this experience. We are contacting the third-party companies selling premium-rate content to ensure that the customer's number is no longer subscribed and we will be refunding the customer in full."
PhonepayPlus regularly monitors companies to ensure they are keeping to its code of practice.
"There is clearly a problem with some of these subscription services," Mr Towler said.
"The vast majority of services are operated in a compliant way, people do like to enter these competitions, and things like that.
"We are in the process of discussions with the industry, and we are going to be issuing a consultation later this month about some possible additional protections, specifically relating to these types of services."
Anyone charged for a premium rate text which they do not remember signing up for, can usually text STOP to the number to end the subscription. The advice is also to contact the service provider and report it to the regulator PhonepayPlus.
Rules should be strengthened to avoid mobile users being hit by unexpected charges on premium rate texts, a regulator has said.