In 2005, he became a parliamentary assistant to Franck Gilard, the member of the National Assembly for Eure's 5th constituency; Lecornu was, at the time, the youngest parliamentary assistant in the National Assembly.[2] In 2008, he became an advisor to Secretary of State for European Affairs Bruno Le Maire; at age 22 Lecornu was the youngest advisor to an official in the government of Prime Minister François Fillon.
He is a member of the National Gendarmerie operational reserve with the rank of lieutenant. He was appointed colonel as a reserve specialist in the fall of 2017.
Lecornu highlights his refusal to raise taxes and rigorous management of public money. Mediapart points out that the hunt for RSA fraudsters has been - with great communication support - the flagship policy pursued by the department since the arrival of Lecornu. It is also closing two priority education colleges, which it justifies by their low occupancy rates.[3]
Nicolas Hulot delegated issues related to energy in general to Lecornu. In particular, he was entrusted with several sensitive files such as the closure of the Fessenheim Nuclear Power Plant, the opening of the Flamanville's EPR, or the Cigeo nuclear waste landfill project in Bure.[5]
On 14 January 2019, Lecornu was appointed with Emmanuelle Wargon to lead the "great national debate", organised in order to get out of the crisis caused by the yellow vests movement.[7]
Minister of the Overseas
On 6 July 2020, Lecornu was appointed Minister of the Overseas in the Castex government.[citation needed] In this capacity, he held crisis talks on the French Caribbean territory of Guadeloupe in late 2021, in an effort to defuse tensions amid unrest stemming from the government's handling of the COVID-19 pandemic there.[8] He also announced that France would be willing to discuss autonomy for Guadeloupe.[9]
Minister of the Armed Forces
Lecornu with US Secretary of Defense Lloyd Austin in 2022
Early in his tenure, Lecornu and Minister of Foreign Affairs Catherine Colonna travelled to Niger together to seal a regional redeployment, making the country the hub for French troops in the Sahel region.[10]
After Ukraine was invaded by Russia in 2022 and NATO allies were in the midst of supplying arms to Ukraine, Lecornu stated at the end of December 2022 in an official visit to Kyiv that the two problems of maintenance and training were the reason for which the Leclerc tanks would stay at home. There were other troubling signs that all was not well with the effort to aid Ukraine. For example, although the CAESAR mobile artillery system had proven very useful to the June 2022 bombardment and recapture of Snake Island and dominated the battle elsewhere, the Ukrainians were having difficulty with the maintenance of the 18 systems and the solution was problematic. Ukrainian defence minister Oleksiy Reznikov hoped that French tradesmen could be sent to Ukraine to service the artillery pieces.[11]
Military procurement
In December 2022, Lecornu and Mariusz Błaszczak signed an agreement between France and Poland on the 575 million euros ($611.69 million) sale of two Airbus Defence and Space observation satellites to Poland.[12]
In March 2024 Lecornu was pleased that Les Forges de Tarbes would henceforth have the capacity to produce 4,000 artillery shells per month.[13] It produced 1,000 per month as of February 2022, the start of the Russian invasion of Ukraine.[14] In March 2024, according to Lecornu, the Russian war machine was able to fire between 10,000 and 15,000 shells per day in Ukraine.[14]