Entire launched the database in 2003, combining its own Open UK database and in-house validation file with the Electoral Roll.
Damian Coverdale, sales director of Bath-based Response One, said: "This is a wonderful opportunity for us. Entire UK offers exciting and largely untapped targeting opportunities and with a pool in excess of 16m the potential for our clients is vast."
Entire's managing director Ian Stockley said Response One was appointed to sell Entire UK to a wider range of markets.
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