The three billion euros of government funding will be spent on transport, urban renewal, security, education and jobs.
Among the measures is a pledge to dispatch 80 extra police officers to the city by the start of 2014.
Although the city's year as European capital of culture has been widely praised, rundown estates in the north of Marseille are plagued by drug-related crime and violence and there have been 24 murders, mostly gang-related, this year.
Police unions say that extra police alone will not solve the problems in a city where unemployment remains above the national average and more than one fifth of residents live below the poverty line.
Unemployment on some housing estates is 40 per cent, a figure that has been blamed for tempting some young people into crime.
Marseille's transport system will receive an estimated 2.5 billion euro, with particular focus on expanding the metro system as well as the construction of an underground train station.
With council elections coming up next year, Ayrault's Socialists hope to take control of the city, which has been won by the right-wing UMP in the last three local polls and Menucci was accompanied by his party's candidate for mayor, Patrick Menucci, during his visit.
Marseille's current mayor, Jean-Claude Gaudin, accused the prime minister of trying to bribe the electorate and claimed that most of the projects were his own proposals.
"This visit is no more than an election campaign tour to support the Socialist candidate," he said.