Pope Francis has criticised US bishops for failing to show unity in the face of a sexual abuse crisis, saying internal bickering had to end over the scandal that has damaged the credibility of the American church.

In a long and highly unusual letter sent as US bishops started a week-long retreat to reflect on the spreading crisis, Francis said the handling of the scandal showed the urgent need for a new approach to management and mindset within the church.

The pope wrote: “God’s faithful people and the church’s mission continue to suffer greatly as a result of abuses of power and conscience and sexual abuse, and the poor way that they were handled.” He added that bishops had “concentrated more on pointing fingers than on seeking paths of reconciliation”.

Pope Francis has summoned senior Catholic bishops from around the world to the Vatican next month to discuss the protection of minors, in his latest attempt to come to grips with the abuse crisis which first erupted in the United States.

Before that meeting, US bishops gathered on Wednesday near Chicago for seven days of prayer and spiritual reflection.

“The church’s credibility has been seriously undercut and diminished by these sins and crimes, but even more by the efforts made to deny or conceal them,” Francis said.

The pope said he was so concerned by the situation that he had hoped to attend the US retreat in person, but added that he had been unable to do so “for logistical reasons“.