UUP leader Tom Elliott must be expelled from the Orange Order for attending the funeral of murdered Catholic policeman Ronan Kerr, a clergyman has said.
Although the rules of the Orange Order prohibit members from attending Catholic Masses, no official sanction is being taken.
David McCarthy is a part of the Orange Reformation Group, set up to "put Protestantism back into Orangeism".
The group said: "No Protestant should ever attend Roman Catholic worship."
It said: "Orange Reformation extends its deepest sympathy to the family of Constable Ronan Kerr who was so brutally murdered by IRA as he went about his business.
"However, we were greatly dismayed to see some members of the Orange Order and so-called evangelical Protestants attend his funeral Mass, which is explicity forbidden in the rules of our institution."
It added: "Rules are rules and they must be upheld."
An Orange Order spokesman said it was right for the murdered policeman's family to realise that they had support from every section of the community.
He said: "It was important that the Kerr family understood the widespread support for them throughout the community and the Orange Order offers its sincere sympathy to them on the loss of their brave son."
Mr Elliott and the former UUP deputy leader Danny Kennedy, who's also an Orangeman, publicly attended the funeral of Constable Kerr in Beragh last week.
Mr Elliott is a former county grandmaster of Fermanagh.