Longer unemployment lines - even in Sunbelt cities - are increasing demands here to stem the flow of illegal aliens seeking jobs north of the border.
With Attorney General William French Smith estimating that there are 3 million to 6 million illegal aliens in the country today, critics on all sides are fond of charging that ''the United States has lost control of its own borders.''
But, according to a Rice University economist who specializes in labor issues , the problem isn't simply a matter of inadequate border controls. Prof. Donald L. Huddle says a major part of the problem is inadequate control on US employers' hiring practices.
The Reagan administration has drawn up a package of reforms to deal with both criticisms. The plan would tighten border control and provide emergency detention and deportation powers. At the same time, a two-year pilot program would allow 50,000 ''guest workers'' into the country each year. With this guest-worker system in place, employers caught knowingly hiring illegal aliens would face stiff fines.
Texas Gov. William P. Clements Jr. (R) is urging President Reagan to allow a far larger number of guest workers into the country. He argues that many essential but low-paying jobs will go unfilled unless Mexican workers continue to be available - either legally or illegally.
Governor Clements will meet with Mexican President Jose Lopez Portillo in Mexico Feb. 8 to discuss immigration issues. Mr. Clements also has created a special task force on undocumented Mexican workers to study the problem.
Dr. Huddle agrees that a first step toward any solution is to carry out ''careful studies to determine how serious the problem is.'' He suggests a national picture of the illegal alien problem would emerge from a scientific survey covering Boston, New York, Florida, the Midwest, Texas, and California.
From his own recent study of Houston's booming construction industry, Professor Huddle concludes that American unemployment is being driven up substantially by the influx of illegal aliens.
Huddle expects the problem to become more serious. He says that the proposals offered by the Reagan administration and Governor Clements will simply throw more US citizens out of work.
On the basis of his Houston survey, Huddle estimates that the US contruction industry as a whole is paying $7 billion a year to illegal aliens. He adds that the displaced American workers represent a drain on the US economy through increased unemployment and welfare payments.
The economist asserts that the Reagan and Clements plans ''will be more beneficial to the business community than to any other segment of society.'' Such guest-worker proposals, he says, ''would hold down the employers' costs and increase net profits because wage bills are less for lower-paid and more manageable (alien) workers.''
AFL-CIO Texas state president Harry Hubbard says that illegal aliens ''are l 00 percent of the workers on some construction projects here'' simply because employers can pay them less. Management and law-enforcement officials, he charges, use illegal aliens to break strikes.