The Montreal-based financial services conglomerate, Laurentian Group Corp., has slammed the brakes on expansion of insurance operations in the United States and Britain.

Jacques Drouin, the president and chief operating officer, said operations in both countries must be stabilized and profitability improved before expansion resumes.He said that disappointing results by the company's U.S. and British subsidiaries marred an otherwise healthy financial year. The group reported a 1987 profit of C$35 million, a 41 percent increase, on revenue of C$1.7 billion.

The Laurentian Group has, however, not put all expansion on hold. Last year, it established a foothold in Hong Kong with Laurentian Asia Ltd., which will launch a series of insurance products.

Claude Castonguay, chairman of the board and chief executive officer, said the company is eyeing markets in Taiwan, Singapore and Malaysia.

In Canada, costs related to a tornado in Edmonton and a flood in Montreal reduced profit of general insurance operations in 1987.

Last year, the company's U.S. subsidiary, Laurentian Capital Corp., acquired American Guaranty Life Insurance Co. in Portland, Ore., and Omega Insurance Co. in Seattle.

A higher than expected cost of the acquisition of American Guaranty and a write-down of certain portfolio investments held by Loyal American Life Insurance Co. in Mobile, Ala., contributed to a C$400,000 loss on U.S. operations.

In Britain, the company merged the British business of its subsidiary, Imperial Life Assurance Co. with Trident Life Insurance Co. to establish Imperial Trident Life Ltd. but the cost and management effort were greater than anticipated. The British operations, thus, showed a loss of C$1.6 million, compared with a C$4.9 million profit in 1986.

The group's assets nearly doubled last year to C$15.2 billion. Mr. Castonguay said the assets should reach C$25 billion within five years.