"The fight against jihadism is without doubt the big challenge since World War Two," Manuel Valls said, flanked by the interior and justice ministers.
The Prime Minister said the "phenomenon of radicalization had widely penetrated into society" and that it was so dangerous because it had the potential to grow.
"It has deeply damaged the Republican pact," he added.
One of his new measures is to create a de-radicalization centre in each region of the country to prevent those identified as being vulnerable to falling into the hands of jihadist groups.
Valls said at least half of the new de-radicalisation centres will take people at the request of the judicial authorities. They will be individuals "who cannot be put in prison".
Around 1,600 young people in France are in state-run de-radicalisation programmes. The new scheme aims to bring that number up to 3,600 within two years.
An official report from earlier this year found that around 8,250 people are believed to have been converted to extremist Islam in France - twice as many as the year before.
Around 70 percent of the suspected Islamist radicals were male and 80 percent of the cases were deemed to be "serious".
The government believes 1,500 of France's 66,000-strong prison population have been radicalised.
Valls said last month that hardline Salafist groups were "winning the ideological and cultural battle" among Muslims in France.
Valls said the first de-radicalization centre could be set up by this summer, and within two years there should be ten centres across the country.
The full plan, which will cost an additional €40 million ($45.5 million) by 2018 on top of the current funding, aims to double existing resources spent on trying to help people already in jihadist networks or those likely to join such groups.
Valls said they hoped to target the "weak-willed" who could be persuaded to leave France to join Isis.
A "green number" set up in 2014 which members of the public can can call to make authorities aware of someone who has been potentially radicalized has proved to be a success and will be bolstered by the Prime Minister.
A new "scientific council" will also be set up to carry out research in to the topic of radicalization and will have access to university grants.
The entire plan consists of 80 measures, including ramping up security at sensitive sites, the mobilization of ground troops as well as better support for the victims of terrorism.
Those who carry out terrorist acts will also receive harsher sentences under the new plan, with prison sentences increased from 22 to 30 years, as is the case already for serious crimes including murder, rape and torture of children.
Under the new anti-terror plans, applicants for security-sensitive jobs -- in airports, for example -- will face extra vetting to weed out anyone with extremist sympathies.
The vetting "will be extended to the staff who are preparing major events", Valls said, just over a month before the Euro 2016 football championships begin in France.
In January this year, France announced it was rolling out more "de-radicalization" prison wings, where prisoners who have been convicted of terrorism will be in isolated cells and will be unable to communicate with anyone who they could potentially influence.
The new measures are a response to the deaths of 147 people in jihadist attacks in France last year.
Jihadist gunmen stormed the Paris offices of Charlie Hebdo satirical newspaper and a Jewish supermarket in January 2015, killing 17 people, and then 130 people were killed in coordinated attacks on the capital claimed by the Islamic State group last November.
Both sets of attacks were carried out mainly by French citizens who had become radicalized and fought abroad alongside jihadist groups.