The proportion of US Catholics who regard priests as honest and ethical has plummeted to a record low of fewer than one in three, according to a survey.

The fall of 18 percentage points between 2017 and 2018 is attributed to the last year’s scandals over clerical sexual abuse.

Fewer than half of the Catholics surveyed by Gallup said they had confidence in organised religion, a drop of eight percentage points over the period.

The poll was conducted four months after the publication of a scathing grand jury report into sexual abuse and its cover-up by Catholic priests and bishops in Pennsylvania.

An investigation found that at least 300 priests had abused about 1,000 children and vulnerable adults over 70 years, and that their superiors had either stood by or in some cases actively covered up criminal acts.

Since the publication of the Pennsylvania report, at least 13 US states have opened formal investigations and some senior Catholics, including the archbishop of Washington, have resigned.

Positive views about the honest and ethical standards of clergy have almost halved in a decade, from 61% to 31%, but the most recent figures show the largest annual fall.

Confidence in the institutions of the church fell to 44% last year compared with 52% in 2017, although the figure was above a low of 39% in 2007.

The crisis in the church has been illustrated by a fall in attendance. In 2018, 36% of Catholics said they had been to church in the past seven days, a small drop from the 39% average between 2014 and 2017, but a dramatic shift since 1975 when 75% reported weekly attendance.

However, the proportion of Catholics among the US population has remained relatively stable. Overall, 22% of Americans identified as Catholic in 2018, compared with an average of 25% over the past 70 years. More than half - 52% - said religion was very important in their lives.

Gallup said: “Given the sheer breadth of the alleged and confirmed sexual abuse, the erosion of Catholics’ views of the clergy’s ethical standards is perhaps to be expected. The church’s handling of many of these cases undoubtedly weighs heavily on Catholics’ minds and likely plays a part in shaping their more increasingly negative views of the church and organised religion as a whole.”

Pope Francis has ordered bishops from around the world to the Vatican next month for an unprecedented summit to discuss the sexual abuse crisis. He has been criticised for failing to take decisive action in the face of scandals in many countries.

• This article was amended on 12 January 2019. The original headline wrongly stated that a third of US Catholics think priests are not honest or ethical.

