The slogan on the bus read: “Boys have penises, girls have vulvas. Do not be fooled.”

A Catholic group, Hazte Oir, had planned to take it on a nationwide tour of Spanish cities.

The group said the ban was illegal and that it planned to acquire a new bus.

One message on the side of the banned bus states: “If you are born a man, you are a man. If you are a woman, you will continue to be one.”

It is believed to be a response to posters put up in northern Spain by a transgender rights group, which read: “There are girls with penises and boys with vulvas. It’s as simple as that.”

An outcry arose in various quarters when the bus was spotted in Madrid on Monday.

The Equality spokeswoman for the Spanish Socialist Workers’ Party, Angeles Alvarez, branded the bus tour “a hate campaign based on intolerance”, according to Spain’s El Pais newspaper.

A spokeswoman for socialists on Madrid City Council, Purificacion Causapie, called it “contrary to the dignity and rights of transsexual children”.

She urged the mayor’s office to ensure Madrid remains “a city free of discrimination, violence and attacks on minors”. Madrid City Council said the vehicle could incite hatred.

‘The bus of shame’

Though the outrage centres on its message, the bus has technically been ordered off the roads for breaching municipal rules on outdoor advertising.

Madrid Mayor Manuela Carmena said the City Council wants the vehicle out of the city “as soon as possible”.

The Councilman for Security, Javier Barbero, said on Tuesday that police had contained “the bus of shame”.

The president of Hazte Oir, which translates as “Make yourself heard” has argued that the group has a right to protest against “laws of sexual indoctrination” and the right to freedom of speech.

Ignacio Arsuaga claimed the slogan on the bus states only “a fact of biology that is studied in schools”.