Tesco has suffered a significant souring of opinion on social media over the last few months, according to analysis carried out for The Grocer.

The level of trust expressed about Tesco on Twitter, Facebook and YouTube declined 25.6% between 17 January and 17 February.

And the overall effectiveness of Tesco’s social media strategy - calculated by social media consultancy Sociagility through analysis of its following, reach, receptiveness, interaction and trust - fell 14% between the two sample dates.

The decline came as Tesco’s market share hit a seven-year low last month [Kantar Worldpanel 12w/e 19 February 2012].

“If my score is heading south would that mean my sales and market share are likely to do the same thing? This could be the case,” said Sociagility’s Tony Burgess-Webb.

The study identified M&S as being the most effective on social media.