The Competition Commission said that the acquisition of the Liverpool-based company by Emap can be expected to result in a substantial lessening of competition in the marketplace because Emap would control 70% of the market.
The commission published a provisional report before Christmas indicating that Emap might have to sell off the data business, which it bought in November, because of the resulting reduced competition in the market for the supply of construction project information and contact data in the UK.
In a statement, Emap said: "The business has been operated separately from Emap's core operations pending the Competition Commission's decision, and will now be put up for sale."
Emap, through its subsidiary Glenigan, and ABI are by far the largest providers of this kind of data to the construction industry, which uses the data to win new business.
The commission did consider other remedies including Emap licensing data to a competitor. However, it concluded that licensing of data would be insufficient to allow a new or existing company to become a genuine competitor to the merged company in the near future, whereas the sale of ABI would ensure that Glenigan would continue to face an effective independent competitor.
Diana Guy, chairman of the Competition Commission inquiry group, said: "The merger, by effectively removing the main competitor, would have left the merged company controlling about 70% of the market. Both Glenigan and ABI have been able to raise prices profitably in the past few years even while in active competition."
She added: "It is likely that the merged company would have even more scope to do so and reduce innovation and quality improvements. The other providers of data have very small market shares in comparison and do not provide a realistic alternative for customers. The merger would therefore remove the choice for customers.
The deal, which was negotiated over the summer, would have seen media giant Emap take over ABI's subscription and information bulletins for the construction industry.
The blocked merger has also saved around 150 jobs at the Liverpool-based publishing company because Emap would have moved the offices to the South East.
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