In a note to clients Nielsen says it expects to regain accreditation soon. It did not specify the reason for the MRC’s decision, although it makes mention of a number of problems encountered with the switch to address-based sampling last year.

Nielsen said: “In the transition, we underestimated our targeted sample size, in two of the four measurement periods, but since November 2009 we have consistently delivered on our targets.”

Address-based sampling replaced the previous landline phone-based sample frame to boost coverage of the 30% of the US population who have only a mobile phone or no phone at all.

Nielsen’s local people meter and combined set-meter and diary measurement markets remain accredited.