On the eve of a visit this week by Pope Francis, the Catholic church in Mexico has been accused of bending the rules on marriage for Mexico President Enrique Peña Nieto and his wife, soap star Angélica Rivera, to enhance his image.

According to a special investigation by a weekly newspaper Proceso and the online news organisation Aristegui Noticias, shared with The Guardian, the Church hierarchy fast-tracked a marriage annulment for Rivera, previously married to TV producer José Alberto Castro. They had been married on a beach in Acapulco and had three daughters together.

The claim is that this enabled her to became Peña Nieto's wife in time to enhance his image, 19 months before the elections which saw him become president.

Peña Nieto's first wife, Mónica Pretelini, died in January 2007 from an epileptic seizure.

According to The Guardian, Castro and Rivera's Catholic marriage certificate appears to show a church ceremony took place in a Mexico City parish before the Acapulco beach service. This contradicted claims that the marriage was not valid because it had been on beach not in an authorised place of worship.

Father Hugo Valdemar, spokesman for the archdiocese of Mexico City, insisted there had been no irregularities and said the annulment "followed the proper process".  Valdemar also denied any political motives for granting the annulment.

Pope Francis is expected to address issues such as corruption, inequality and insecurity during his visit to Mexico.