Britain wrings hands over pound

British politicians and economists have a new worry on their hands: Falling oil prices are pushing down the value of the pound on exchange markets. This in turn raises delicate political and economic issues, at a time when the British economy is showing little sign of recovery.

When Britain lowered its North Sea oil prices by 10 percent Feb. 18, it was confident that spot markets had already discounted the move. In addition, sterling had fallen considerably in previous months. Since oil is traded in dollars, the British government has been receiving more and more pounds as the dollar has strengthened.

But the pound has kept falling since the British oil price cut. The cut was followed by an even steeper Nigerian oil price reduction and market speculation that OPEC countries will have to cut considerably more from their own official prices than they had planned.

''On the one hand, a further drop will help offset even lower prices for North Sea oil, which could be forced upon us if OPEC cuts are severe,'' notes a source close to Prime Minister Margaret Thatcher. ''On the other (hand), a significant further fall in sterling will result in higher inflation in Britain in 12 to 18 months from now.''

A cheaper pound makes British exports more competitive and imports more expensive. It also raises the prospect of higher British interest rates to attract speculators back.

The prime minister has said in the long term, she sees lower oil prices as a boost for the world economy out of current recession.

What her advisers worry about is the short term: Will interest rates go up again? They have risen twice since November, much to the prime minister's disapproval. She does not want to see them go up again, and the Bank of England has been instructed to buy enough sterling on the exchange markets to keep it from falling too fast.

Nonetheless, at this writing the pound was hovering around its lowest value ever against the dollar. On the Bank of England trade-weighted index against a basket of three currencies, the pound was at its weakest since June 1978.

For a prime minister who is proud of her record in bringing inflation down, a rise in interest rates is bad news - especially as she tries to decide when to call the next election. It could come in June or October of this year, or even in May of next year, when she will have been in office for a statutory five years.