Less than four  in 10 American Catholics attend mass weekly, a new poll has suggested, meaning Protestants are now more reliable in their church attendance.

The latest study from Gallup shows an average of 39 per cent of Catholics had attended church in the last week from 2014 to 2017, compared with 45 per cent from 2005 to 2008. Even among older Catholics, traditionally more likely to attend mass, less than half now meet the faith's weekly obligation.

It continues the steady decline in Catholic church attendance in America that began with a dramatic 20 per cent drop between the 1950s and the 1970s before steadying to between a four and six per cent decline each decade.

In comparison the roughly 45 per cent of Protestants from 2014-17 remained unchanged from a decade before, meaning US Protestants are now more likely than their Catholic compatriots to attend church weekly.

Even among Catholics aged 50 and older, typically more likely to go to church regularly, only 49 per cent reported attending weekly after a decline of up to 10 percentage points per decade since 1955.

'In particular, older Catholics have become less likely to report attending church in the past seven days – so that now, for the first time, a majority of Catholics in no generational group attend weekly,' the study found.

'A troubling sign for both religions is that younger adults, particularly those aged 21 to 29, are less likely than older adults to identify as either Protestant or Catholic,' the research said. 'This is partly because more young people identify as "other" or with other non-Christian religions, but mostly because of the large proportion – 33 per cent – identifying with no religion.'

However when it came to the proportion of the American population identifying with each faith, Catholics maintained the upper hand over Protestants.

While the rate at which Protestants attend church has remained steady, the number saying they are Protestant has declined drastically from 71 per cent in 1955 to 47 per cent in the mid-2010s. By contrast the Catholic population in America has remained consistent, largely thanks to the growing Hispanic population, although fewer go to church. Twenty-two per cent of US adults today identify as Catholic, compared with 24 per cent in 1955.