President Emmanuel Macron of France is stuck in a “ketchup moment” whereby the effects of his reforms are still stuck inside the bottle but with a “thump” will soon come flying out in one go, his interior minister has claimed.

Gérard Collomb, the interior minister, issued the ketchup analogy to explain the lack of tangible benefits of Mr Macron’s reforms while also dealing his presidency a fresh blow by announcing his intention to step down next year to run for re-election as mayor of Lyon in 2020.

His reference to the physics of the famed bottled tomato sauce came a day after an MP quit his party, saying she felt as if she was “on the Titanic”.

Frédérique Dumas resigned from Mr Macron’s centrist Republic on the Move party because she said the government had “forgotten the fundamental principles of Macronism”. She added: “Some decisions come down to budget cuts. There is no ambition, no direction.”

The move by Ms Dumas, 55, a former film producer, reflects growing disillusionment with the president and impatience that his controversial and often painful economic reforms have so far failed to cut unemployment or significantly boost growth.