Nuisance calls to mobile phones are on the increase, with many people not realising they could register their number with the Telephone Preference Service (TPS), according to research from Which?
One in 10 (10%) mobile phone users reported they had received more than 20 unwanted calls in the space of a month.
The findings from a survey of more than 2,000 people also indicate that nuisance calls to mobile phones are on the rise - with seven in ten (72%) people saying they had at least one such call to their mobile in the last month compared to more than half (55%) in 2013.
Which? said that Ofcom and TPS data shows that of the 78.9 million active mobile phone subscriptions in the UK, just 3%, or 2.4 million, are registered with the TPS.
Which? has worked with the TPS to launch a new free text service which helps people to register their mobile phone numbers to stop unwanted calls.
People can register their mobile phone with the TPS for free by texting OPTOUT to 80057 and Which? will send them details of the steps to follow so that they can stop nuisance calls.
The TPS is the free, central opt out register on which consumers can record their preference not to receive unsolicited sales or marketing calls.
The TPS can accept the registration of mobile numbers as well as landlines in order for a consumer to stop receiving marketing calls.
Which? found that only around a third (36%) of people knew that the TPS could be used to block unsolicited calls to mobiles compared to almost all (96%) who knew it could be used with landlines.
The consumer group's executive director, Richard Lloyd, said: "With the number of nuisance calls to mobile phones on the rise, it's vital people register their phone if they want to help protect themselves from this everyday menace.
"The Government, regulators and business need to continue to work together to tackle nuisance calls, with further action to cut them off at source and make senior executives accountable if their company is caught flouting the rules."