Brussels, 17/12/2003 (Agence Europe) - As announced yesterday, the European Commission has adopted guidelines on the appraisal of mergers between competing firms (Horizontal Guidelines). The guidelines are one of the cornerstones of the comprehensive reform of merger control greed by the Council on 27 November and which should enter into force on 1 May 2004, following final authorisation by the Council planned at the end of this year. The European Commission indicates that it has adopted guidelines that describe in detail the analytical approach it takes when assessing the likely impact on competition of mergers between competing, or potentially competing, firms. The guidelines make it clear that mergers and acquisitions will be challenged only if they enhance the market power of companies in a manner which is likely to have adverse consequences for consumers, notably in the form of higher prices, poorer quality products, or reduced choice. The guidelines make it clear that mergers and acquisitions will be challenged only if they enhance the market power of companies in a manner which is likely to have adverse consequences for consumers, notably in the form of higher prices, poorer quality products, or reduced choice. Of course, for the Commission to be able to take into account any efficiency claims, the merging parties will need to prove that the efficiencies are merger-related and will benefit consumers. Other factors that might mitigate an initial finding of likely harm include such cases where there would be no barriers to entry in the market; where customers in a given industry enjoy significant "buyer power" or when the elimination of a ailing competitor would occur even absent the merger with the same or worst anti-competitive results The Guidelines will be published as soon as the Council will have formally adopted the new Regulation, at the same time as the publication of a set of best practices for the conduct of merger investigations.