Holcim Ltd said on Monday it has filed with the French financial market regulator details of its proposed share exchange with Lafarge.

The offer allows Lafarge shareholders to exchange all shares in the Paris-based company for newly created shares in Holcim. The exchange ratio is 10 Lafarge shares for nine shares in Holcim.

Two thirds of Lafarge's 293 million shares have to be offered up by shareholders for the deal to go ahead.

The offer is due to open on 1 June and run until 3 July. If successful, the offer will then be reopened to any remaining Lafarge shareholders to offer up their shares.