Opposition to border checks on the Northern Irish border is substantially higher among Catholics than Protestants, new research reveals, with one in 10 Catholics backing illegal protests.

It comes as Theresa May faces a feud in her Cabinet over plans for a customs partnership after the UK leaves the EU. Under one proposed model, known as 'maximum facilitation', some form of border checks would be required on or near the border between the Republic of Ireland and the North.

There is strong opposition to such checks on the north-south border and also the east-west border between Ireland and mainland Britain, a report published today by academics from Queen's University Belfast found.

'There are strong expectations that protests against either North-South or East-West border checks would quickly deteriorate into violence,' the report says.

One in five Catholics find the muted option of camera-based border technology 'almost impossible to accept'. This rises to 72 per cent who would find British soldiers manning checkpoints 'almost impossible to accept.'

Over a fifth of Catholics would support protesters blocking traffic and nearly one in 10 Catholics would support cameras being vandalised. One in 10 Sinn Féin supporters would support border infrastructure or installations being attacked.

The option of the UK as a whole remaining in the customs union and the single market is preferred by 61 per cent of Catholics (including 68 per cent of Sinn Féin voters), and 62 per cent of Protestants (including 58 per cent of DUP voters).

Following on from fears that Brexit could split the United Kingdom, forcing a referendum either on Scottish independence or Irish unification, the survey revealed there is substantial support among Catholics for the idea of having a referendum on a united Ireland (68 per cent in favour compared to just 29 per cent of Protestants in favour) once the UK has left the EU.

It comes after Christian Today reported that the border issue may have scuppered chances of a historic trip to the north by Pope Francis when he visits Ireland in August. Many in the region and elsewhere had hoped that the pope would visit Northern Ireland, deemed too sensitive back in 1979 when John Paul II came to the Republic. But there was no mention of the North in the official announcement of the trip in March.

One senior Vatican source told CT's James Macintyre of the issue last year, when the trip was being planned: 'It complicates things quite a bit'.

This is because the concept of a divided Ireland is anyway controversial, especially among Catholics, and a visit by the pope at a time of political uncertainty and unrest could be seen as an endorsement, however faint, of the concept of that divisive, hard border.