Despite persistent attempts by European energy policy-markers to play down the gravity of the oil supply crisis sparked by the troubled political situation in Iran, major oil companies based in the common market clearly think otherwise.

A top executive with a leading oil multinational contacted here claims privately that, even with offsetting increases in exports from Saudi Arabia and Iraq, the drop in Iranian crude exports plus the severe climatic conditions hitting Europe this winter mean that stocks are being drawn down by as much as 5 million barrels per day more than in a normal winter.

As a result, if the Iranian situation is not suddenly and dramaticall stabilized before the end of the month, the oilman concludes that the first "crunch point" in oil supplies for the non-Communist world will come by the end of the first quarter of this year.

Moreover, a second and more serious crunch point could come early next winter, since stocks, which by April will have become "uncomfortably low" will not be replenished by then unless in the meantime there is a remarkably rapid recovery in the volume of Iranian exports, according to the executive who has recently met with Middle East leaders including oil minister Sheik Yamani of Saudi Arabia. Saudi Arabia has made clear that its extra one million barrel per day contribution to the West's oil import needs will not continue beyond the first quarter. Under these conditions "stocks could not be replenished by year end, oil would be tight," and prices would rise beyond the hikes already set by OPEC, say oil company officials.

Faced with this potentially grim prospect, industry sources admit that "it's up to governments to work out how they want to put the message across," But the clear inference is that the "no panic" approach presently being adopted by the Paris-based International Energy Agency and European Economic Community (EEC) energy boss, Commissioner Guido Brunner conceals a much harsher reality -- particularly for the nine-nation European community, heavily dependent on external supplies of oil.

Europe's public authorities appear to be striving to stem the spread of economic panic. "We need a steady nerve in this sort of situation," admonishes Brunner, echoing the warning made last weekend by IEA Executive Director Ulf Lantzke, against "undue alarmism" over the oil situation. Lantzke's remark was prompted by a statement attributed to Royal Dutch Shell, the largest European oil company, that supplies were now being hit as badly as during the 1973-74 crisis.

But, note observers here, the level of industry concern appears to correspond to the testimony of U.S. Energy Secretary James Schlesinger made in recent Senate hearings.

The EEC's "keep cool" attitude is further pointed up by Brunner, who appears to predict a positive outcome to the Iranian troubles. "I don't believe that the Iranians can do without revenue from oil exports which they need to finance their extensive industralization program, maintains the EEC's chief energy policy-maker.

Sounding a more laconic note, European diplomatic sources also stress that it is the oil industry that stands to gain by fostering the conviction of an imminent supply crisis followed by higher prices. Quotes for gasoline on the Rotterdam spot market have almost double the levels pertaining before the Iranian troubles.

Yet behind the scenes, European governments and officials are clearly preparing to meet the full impact of serious oil supply shortages. A special EEC crisis committee, including high energy officials from nine European governments, have held a series of meetings to monitor international market developments. They meet here next week in another closed session, reveal sources close to Brunner.