Some telemarketers initially claim to be carrying out market research - you only realise later in the conversation that they are calling to sell you something. This is called ‘Sugging’ (selling under the guise of market research).
You may receive calls from genuine market research companies. They are allowed to call you even if your number is on the Telephone Preference Service list, but will stop calling you if you ask them.
For more information you can contact the Market Research Society.
Unwanted Market Research calls can be blocked by trueCall.