IT is unfortunate that circumstances have made Britain think it must leave UNESCO - the United Nations Educational, Scientific, and Cultural Organization - unless that agency initiates major reforms. By its action, Britain joins the United States in a challenge to UNESCO's leadership, in particular, Director General Amadou Mahtar M'Bow of Senegal, who was elected to a second seven year-term in 1980.
The conservative-led governments of the United States and Britain argue that UNESCO is financially mismanaged and has become excessively politicized - resulting in an anti-Western bias. They have a point. UNESCO should take the criticism to heart and put its house in order.
The US plans to go ahead with its earlier decision to withdraw from UNESCO next month. Britain has threatened to pull out by late next year. Actual withdrawal of the two Western nations would add up to a severe blow, since they contribute 33 percent of UNESCO's budget.
It is important that all parties to the dispute work out a reasonable compromise. Some efforts along that line have already begun. At an executive board meeting this past September, UNESCO agreed to a zero-growth budget. That had been a key objective of the United States. Moreover, UNESCO officials have hinted of late that they are willing to be more circumspect in promoting the ''new world information order'' that has been an important part of their policy agenda. The United States and many Western news organizations are justifiably concerned that such an information system would constitute press licensing and censorship in third-world nations.
The immediate effect of Britain's decision is to impose new pressure on Director General M'Bow, who has insisted that he will complete his current term. But the decision also raises new strains within the Western alliance, since other European nations, including the West Germans and Danes, have urged Britain to work for reform within UNESCO, rather than join the United States in leaving it or threatening to leave it.
For all of the anti-Western polemical zeal that often emanates from the agency's headquarters in Paris, UNESCO performs many essential tasks on the world scene. It trains teachers for poor nations. It has undertaken projects to save world monuments. It fights illiteracy. It fosters important oceanographic and environmental research.
There are precedents, of course, for strong US action. When the Carter administration left the International Labor Organization back in 1977, it led to a number of structural changes in that agency. The US rejoined the ILO in 1980.
Still, the better way would be for the US - and Britain - to remain within UNESCO and work for changes inside the agency. UNESCO's executive board is scheduled to meet early next spring. But there is still time for the agency, and the US and Britain, to work out some mutually acceptable compromise that would make withdrawal unnecessary.