The French prime minister, Manuel Valls, will put his political career on the line on Tuesday afternoon by seeking a crucial vote of confidence from parliament in his programme to tackle the country's economic woes.

Valls, who formed a new government less than four weeks ago, needs to quell dissent that has caused bitter divisions in the ruling Socialist party (PS) and overcome president François Hollande's record unpopularity, to obtain a clear mandate from the lower house, the Assemblée Nationale.

He is expected to win the vote, but will need a very clear majority to silence the critics and give him enough support to push through proposed reforms. A narrow victory could leave parliament paralysed just weeks before the government seeks approval of its 2015 budget bill.

Rebel MPs on the left of the party, known as frondeurs, have threatened to derail the government by abstaining in protest at what they see as its lurch to the centre right.

Valls has insisted France make swingeing public spending cuts and ease taxes on businesses to promote employment and growth, which the rebels see as taking a social democrat rather than socialist political line. They want the government to reject EU demands that France reduce its deficit and to shun austerity measures.

Among the frondeurs are the former finance minister Arnaud Montebourg, the former education minister Benoît Hamon and the former culture minister Aurélie Filippetti of the Green party, all of whom were sacked from the cabinet after publicly criticising the government.

Valls was expected to ask Socialist MPs to put aside their differences and vote for the government at a meeting on Tuesday. Between 30 and 40 have threatened to abstain, but Valls has not ruled out "an accident" with up to 60 ignoring his appeal and leaving the government floundering.

Valls needs a majority of 289 votes from the 577-seat assembly. This is exactly the number of Socialist MPs following the recent expulsion of Thomas Thévenoud, the junior foreign trade minister sacked after nine days for having failed to pay his taxes.

Valls will be hoping for support from the Ecologists - who have 18 MPs but no longer have anyone in government, and have not yet decided which way to vote - and from the Front de Gauche and Communists. who have 15 MPs but are not inclined to support Valls's administration, seeing him as a French Tony Blair. At least 199 opposition UMP MPs and 30 MPs from the centre-right UDI party are expected to vote against the government.

The French PM can still get by with a relative majority of 286 votes, but his position would be weak and the government could have difficulty pushing through major legislation.

If he loses the vote he will be forced to present the government's resignation. Hollande can then ask him, or someone else, to form a new government or call a snap election in which, given the level of disillusionment with Hollande, many Socialist MPs would lose their seats.

Political experts have described this as a kamikaze option and say it is unlikely. No French government has been overturned by a vote of confidence.

Madani Cheurfa of the thinktank CEVIPOF, which is attached to the respected Sciences-Po Institute of Political Sciences, does not believe the government will fall.

"If the Socialists turn against Hollande, they will have to go back to the ballot boxes and risk defeat. In this case they've everything to lose by abstaining, so they probably won't," Cheurfa said.

Political scientist Philippe Braud told AFP he thought the vote was still likely to pass "because the fear of catastrophe is still the best source of unity".

It has only happened once in the Fifth Republic, in 1962 when the then prime minister Georges Pompidou was handed a motion of censure, forcing president General De Gaulle to dissolve the Assemblée Nationale and call a general election. Pompidou won.

While Hollande would not be toppled if the vote is lost, his position would be fatally weakened at a time when a series of polls show that up to two-thirds of French voters want him to stand down before the end of his term in 2017.

Waiting in the political wings are the former president Nicolas Sarkozy, who is expected to announce his comeback before the end of this week, and Marine Le Pen, head of the far-right Front National, whom polls suggest would beat Hollande in a second-round presidential runoff.

Valls is to present his programme to the French lower house on Tuesday afternoon, followed by a debate and the vote of confidence. He will go on French television at 8pm on Tuesday evening.

On Monday, Valls told TF1 television the vote would be "a dramatic moment, but a good one".

"I'm confident," he added. "We will continue to govern right to the end."