An anti-transgender bus has been forced out of Madrid after activists, trade unionists and city council members rallied together against its message of intolerance.

The bright orange vehicle was first seen in the capital city Monday when a group of concerned citizens noticed an offensive slogan on its side: "Boys have penises, girls have vulvas. Do not be fooled. If you are born a man, you are a man. If you are a woman, you will continue to be one."

Commissioned by Catholic group Hazte Oir (Make Yourself Heard), the bus was scheduled to go on a nationwide tour of the country's major cities.

It's believed that the tour was launched in response to posters put up in northern Spain promoting inclusion and acceptance of trans youth, which read: "There are girls with penises and boys with vulvas. It's as simple as that."

Once news of the bus campaign began to spread, the cause was quickly picked up by ranking city officials.

Angeles Alvarez, equality spokeswoman for the Spanish Socialist Workers' Party, branded the tour "a hate campaign based on intolerance." City council member Purificacion Causapie added: "[The campaign is] contrary to the dignity and rights of transgender children."

By Tuesday, the vehicle was removed from the city, with police saying they'd "contained the bus of shame."

Hazte Oir president Ignacio Arsuaga countered the removal by saying the slogan merely states "a fact of biology that is studied in schools." He went on to say that curbing the bus violates the group's freedom of speech.

"The Madrid City Council kidnapped the bus this morning, with no legal order from any court. This is illegal, and our lawyers are preparing a complaint so that our right to freedom of expression is restored," he told the BBC.

"We are going to appeal this unjust decision and file a criminal case against the extreme-left Madrid mayor."

In anticipation of the group's arrival in her city, Barcelona mayor Ada Colau released a preemptive warning on Twitter: "In Barcelona there is no place for LGBT-phobic buses. We want our children to grow in freedom and without hatred."

In spite of the cold reception its bus received, the anti-LGBT group unveiled a brand new transphobic vehicle Thursday afternoon, which they parked outside of the main administrative building in Madrid.

Though Spain's majority Catholic church continues to rail against the queer community, the country itself has long been at the forefront of LGBT equality, legalizing same-sex activity in 1979, establishing anti-discrimination protections in 1995 and passing marriage equality in 2005.