SEATTLE — As the Seattle City Council begins Thursday to debate Mayor Ed Murray’s plan to increase the minimum wage in the city, tensions are growing between labor and business groups.

Despite an agreement already in place, business groups are lobbying for more changes. The agreement, forged after five months of negotiations among labor, employers and nonprofit representatives in an advisory committee, appeared to have support when it was revealed earlier this month.

The plan gives businesses with more than 500 employees nationally at least three years to phase in the increase. Those providing health insurance will have four years to complete the move. Smaller organizations will be given seven years, including a consideration for tips and health care costs over the first five years of the phase-in.

But now, business groups are pushing for a training wage, a longer phase-in for nonprofits of any size, and no minimum wage for employers with less than 10 employees. Their proposals were expressed in a letter prepared by City Council staff.

Labor representatives from the advisory committee countered back in their letter sent to the City Council. They said the council should pass the plan already approved.

They also expressed discontent that City Council staff prepared the business-friendly proposals, saying that the staff should have included worker-friendly proposals.

“If the Council intends to consider different options, we would expect it to consider pro-worker options supported by the public and not only employer friendly options. That said, we want to be clear that we believe the mayor’s compromise proposal remains the best way forward,” the letter said.

The letter outlined a few “pro-worker” changes, including not counting tips toward compensation, shortening phase-ins and eliminating training wages.