Mr Marshall could not confirm that competency service increments (CSI) would be secured in the negotiations.
Police Minister Anne Tolley has said the ministry wanted to provide more support for frontline staff, and they would not be affected by this year's budget.
But with no new money allocated to police, the Opposition said the Government would come under huge pressure if a pay rise was secured.
Labour Party police spokesman Kris Faafoi said wages made up 70 per cent of total police spending.
"They are going to have a huge problem with their budget if they end up coming out of those negotiations with a higher wage bill," he said.
Police have predicted that a 3 per cent wage increase would cost $75 million a year and CSI increases would cost $42.5 million a year.
In a tense select committee yesterday, Labour MP Phil Goff attacked the Police Minister for her refusal to answer questions on police wages and possible station closures.
He argued that the police operating budget had increased by $8.9 million but police faced inflation costs of $24 million - a deficit of $15 million.
Ms Tolley repeatedly deflected his questions, saying she did not want to influence the negotiations.
"I have no responsibility for how the police meet their budget - that is an operating issue."
When he repeated his argument that police faced a deficit, Ms Tolley replied, "That's life, Mr Goff".
After the meeting, Mr Marshall insisted that no police stations would be closed, but he said stations were continually being assessed for their "appropriateness".
A letter leaked to the Police Association in May claimed that the force wanted to introduce performance-based pay and scrap general salary increases.
Mr Marshall said yesterday that police did not intend to "go back to the 1990s".