The FNV and CNV trade unions are to escalate the dispute with Shell on Wednesday when workers at the oil giant's NAM plants in The Hague and Emmen will begin cutting production. A spokesperson for CNV Bedrijvenbond said production at the two NAM petroleum plants would be reduced by half. The industrial action at NAM will not have any impact on the public at this stage. Workers at Shell's Pernis refinery in Rotterdam and the Moerdijk petrochemical plant in North Brabant began shutting down production on Monday evening. Pernis produces 418,000 barrels per day and is Europe's largest refinery. For safety reasons, the plants can not be shut down immediately. The gradual process will take two weeks.The dispute involves changes to the pension schemes for about 9,000 Shell employees and 1,800 workers at NAM. Shell's reforms would have employees paying pension contributions - something they have not done for years. The company also wants to increase the retirement age. The FNV argued last week that the Shell pension fund is financially sound and there is no reason for what the union describes as "cost-cutting measures". Shell rejected this description and said the plan relates to "future cost management". Giving in to the union demands would add 9 percent to the company's annual wage costs, Shell claimed.