** Shares in Germany's Heidelberg Materials AG HEIG.DE and Swiss firm Holcim AG HOLN.S drop between 4.5% and 5.5%, and trade at the bottom of their respective blue-chip indexes DAX .GDAXI and SMI .SSMI
** UBS points to a Handelsblatt report according to which the European Commission is planning to significantly weaken the ETS emissions framework by increasing the number of available emission certificates and delaying the end of auctions
** The European Commission would present its proposal in July, Handelsblatt adds
** Heidelberg Materials is "widely seen as a decarbonisation leader and a relative winner of a tightening EU ETS", as it stands to "benefit from positive industry pricing effects and is expected to enjoy cost advantages versus peers", Metzler analyst Thomas Schulte-Vorwick says
** "A softening of the framework is therefore likely to be perceived negatively by investors," he adds, noting however that the report lacks concrete details on the scale and feasibility
** If losses hold, Heidelberg Materials and Holcim's shares are on track for their worst day since last April
(Reporting by Emanuele Berro)
((emanuele.berro@thomsonreuters.com))