The French military command and the government have vowed to punish active officers and force rightwing reservist generals into full retirement for signing an incendiary declaration mourning the “disintegration” of France because of Islamist radicalism and immigrant “hordes” in the suburbs and hinting at a coup d’état.

Published last week in the rightwing magazine Valeurs Actuelles (Today’s Values) on the 60th anniversary of an unsuccessful generals’ putsch against Charles de Gaulle aimed at keeping Algeria as part of France, the inflammatory statement was at first dismissed by the authorities as an outbreak of eccentric nationalist nostalgia by octogenarian retirees.

But it soon emerged that at least 18 active military personnel were among the thousands of signatories, while far-right leader Marine Le Pen — who is shown by opinion polls to be Emmanuel Macron’s main rival for the presidency in next year’s election — endorsed its thinly veiled call to arms.

“These are grave times, France is in peril,” the declaration said. “Know that we are ready to support politicians who will take into account the need to preserve the nation . . . If nothing is done, laxism will continue to spread inexorably in society, provoking in the end an explosion and the intervention of our active comrades for a dangerous mission to protect our civilisational values.”

Le Pen said she agreed that “it was the duty of all French patriots, wherever they are from, to rise up to restore — and indeed save — the country”, although she emphasised that the struggle should be political and peaceful.

General François Lecointre, armed forces chief of staff, said the leading signatories had retired 20 or 30 years previously, but there were also 18 active personnel — four of them officers — among those who signed. They would be punished according to their level of seniority, while the generals who are no longer active but can be called up as reservists would be compulsorily forced into full retirement.

“It’s an exceptional measure, that we will launch immediately at the request of the defence minister,” he told Le Parisien in an interview.

“At first I said to myself that it wasn’t very significant, and then that the authors knew very well that they were taking a political position. That I cannot accept, because the neutrality of the armed forces is essential. But then I was shocked to read there a call to active soldiers: I find that repulsive.”

Lecointre singled out Christian Piquemal, the former head of the French Foreign Legion, for particular criticism. Piquemal had already been forced into full retirement five years ago for having taken part in an illegal demonstration against immigrants in Calais.

Jean Castex, prime minister, condemned the declaration after the weekly cabinet meeting on Wednesday, saying it was “contrary to all our republican principles”, and criticised Le Pen for her “unacceptable” exploitation of the controversy for political reasons.

Florence Parly, defence minister, said on Twitter that Le Pen’s support “reflects a serious misunderstanding about the institution of the military, which is worrying for someone who wants to become commander-in-chief”.

There have long been concerns on the French left about the level of support for the extreme right in the police, gendarmerie and armed forces, although some recent elections — for example, the European elections of 2019 — suggest Marine Le Pen’s Rassemblement National is also the most popular single political party in the country as a whole.

A Harris Interactive opinion poll for LCI showed 58 per cent of French voters polled supported the military officers who signed the controversial declaration, compared with 42 per cent who were opposed.

Chart showing results of survey on support for the military signing the controversial declaration warning of the ‘disintegration’ of France

Among respondents who said they supported a political party, 86 per cent of RN sympathisers backed the soldiers. For the centre-right Les Républicains party, support was at 71 per cent, and even in Macron’s La République en Marche party it was at 46 per cent.