The families of some victims of the Omagh bombing, in which 29 people died, have announced that they will boycott a ceremony to mark the tenth anniversary of the atrocity.

The decision introduced a note of discord to attempts to provide a dignified commemoration of the event in 1998, which is regarded as one of the worst incidents of the Troubles.

The size of the death toll, and that it took place as the Northern Ireland conflict seemed to be subsiding, means it has stayed high in the public consciousness in Ireland and further afield.

It has also been kept in the public eye by the Omagh Support and Self Help Group, which has been involved in high-profile publicity and legal battles, and by the production of a feature film.

Yesterday, the group said it would have no part in the commemoration to be held on Friday next week, claiming it had not been consulted by the organisers, the local council. The group will hold its own memorial event on Sunday, instead.

Kevin Skelton, whose wife, Philomena, died in the bombing, said: "There's a whole range of issues I've got problems with. The whole wording issue and some of the politicians that are going to be there – I think the council have made a real mess of it altogether."

Local observers say the council has tried to reach a consensus on the design of a garden of remembrance, which is to have a glass obelisk, and on the wording of a memorial. It appointed an independent committee to advise on the issues, with councillors unanimously accepting its recommendations.

Perhaps unsurprisingly, given the large numbers of people bereaved by the bomb, those affected have not been in complete agreement on how to conduct themselves. Some have said little or nothing in public, while the Self Help Group has, by contrast, pursued a number of avenues.

In particular it has, with government support, launched a multimillion-pound civil action claim for damages from five Republicans, accusing them of being leading members of the Real IRA. The Self Help Group has often been critical of the authorities, saying the Government should launch an independent inquiry into the bombing.

It has also accused the Irish government of making many promises, "but in reality the substance is very little".

Omagh district council's chairman, Martin Mcloughlin, a member of Sinn Fein, said yesterday: "I would love to see everyone there on Friday. As a council we have tried to do our best to mark the anniversary.

"I realise it's a sensitive time and different people will react differently, but I can't legislate for how some families are going to react."

The council's moderate nationalist vice-chair, Josephine Deehan, added: "I very much respect the decision of individual family members not to attend.

"It was always going to be very difficult to get 100 per cent consensus around what the council should or shouldn't do. But we consulted widely and we took the best decision that we could."