Spain's culture minister was only in office for seven days but resigned following local media reports that he had avoided paying taxes while working as a TV journalist 10 years ago.
Maxim Huerta was appointed to Prime Minister Pedro Sanchez's cabinet last week. He says he is "absolutely innocent" and fully up to date with his tax payments.
Speaking at a news conference in Madrid Herta said: "I have paid the fine twice, at the time and now, here," adding the penalty was not illegal at the time.
El Confidencial newspaper reported that Huerta had been found to have avoided paying tax amounting to over €218,000 between 2006-2008,
In a tweet, Maxim Huerta said: "To defend what you love most, sometimes, it is necessary to withdraw."
A new era for Spain
Huerta's resignation comes just weeks after former prime minister Mariano Rajoy was ousted from his position in a confidence vote over a long-running corruption scandal that tainted the conservative Popular Party,
Huerta said he was stepping down to protect the new Socialist government of Prime Minister Perdo Sanchez from criticism.
For the first time in Spain's history, Sanchez has appointed more women than men in ministerial posts.
Opinion polls show his PSOE party has rebounded since taking power, overtaking rivals such as Ciudadanos and Podemos, which had poached its voters in recent years.
But it will be difficult for Sanchez to make any major policy changes, as he controls less than a quarter of the seats in parliament.