A group of labor leaders suggested yesterday that the government help reduce unemployment by cutting five hours from the standard 40-hour work week.

The leaders endorsed legislation, introduced by Rep. Conyers Jr. (D-Mich.), which would:

Require that, by 1983, employers pay overtime to eligible employes after 35 hours a week, instead of 40 as now.

Increase the required compensation for overtime to double time from the required time-and-a-half paid now.

Give employes the legal right to refuse overtime work, except in emergencies (war was given as one example).

The bill is before the House subcommittee on labor standards, which yesterday opened three days of hearings on it.

"Historically, the reduction of working hours has been a major method for spreading work and spurring new employment," Conyers said.

"Major avenues of potential new employment have been closed because employers have refused to hire new workers and in many industries have been able to compel their employes to work overtime, regardless of artitrariness in scheduling," Conyers said.

No labor leader who spoke before the panel yesterday dissented from that view.

Rudolph Oswald, research director for the AFL-CIO, said his organization has supported the concept of a shorter work week since 1961. In 1977, at its 12th constitutional convention, the AFL-CIO, endorsed a proposal identical to Conyer's, Oswald said.

He said the proposal could especially benefit families in which both spouses work by allowing them to spend more time at home and eliminating the fear of disrupting family schedules through mandatory overtime labor.

"Workers bitterly resent being disciplined for refusing to work overtime," Oswald said. He added: "A reduction in the standard 40-hour work week is long overdue."

But such a reduction would also be inflationary, forcing employers to pay higher salaries for shorter hours and driving up costs in service industries, said Rep. John N. Erlenborn (R-III.), a subcommittee member.

"I really have some problems with this legislation," Erlenborn added.