A slip and fall at last year's national Anzac Day parade has prompted the Returned Services League (RSL) to reduce the role of young children in the march in Canberra.

A letter to prospective participants in the march from the president of the RSL's ACT branch, John King, emphasised "the march is for veterans and current serving members of the ADF".

As such, Mr King said relatives of deceased veterans "should not march", but they have not been banned.

Kids under 12, on the other hand, will no longer be allowed to walk down Anzac Parade alongside veterans, after the RSL was told the public liability insurance would no longer cover them.

In the 2017 parade, a child tripped and took down an elderly person they were marching with, who was then treated by paramedics.

Children under 12 will operate as greeters and in other pre-march activities. ( AAP: Alan Porritt )

Mr King said it was understandable that the public liability insurance would no longer cover the youngest marchers, who are also banned from riding in vehicles, and the youth groups the RSL had spoken to had "accepted the issue".

"We've set the age of 12 as an age limit that we feel children can reasonably understand what's going on," he said.

"[They can] be more across what's going on and if they have to manage the person as a carer, that's reasonable.

"We've also spoken to the youth groups through our liaison officer and they've accepted the issue."

Kids can participate once they're capable, RSL ACT says

About 7,000 people attended last year's march in Canberra. ( ABC News: Elise Pianegonda )

The younger members of the various youth groups involved will have a role, handing out rosemary and greeting people entering the parade.

On an invitation to their members, the Girl Guides said participants aged 5 to 11 will hand out rosemary and form a guard of honour but that was where their involvement would end.

Many children may be relegated to spectator roles in Canberra this year. ( ABC: Rob Reibel )

"Instead of joining the march as in previous years, they will go back to the Guide tent to be picked up," the invitation read.

"We understand that some Guides will be upset as they won't be able to take part in Anzac Day as they had expected.

"We should feel honoured that we are included on the day in whatever capacity is required."

Mr King said the changes made were always "trials" and they would re-assess after the event.

He also rejected the suggestion this move would stop young people from engaging with Australia's military history.

The RSL ACT branch president said even those not allowed to march would still be engaging with the military's history. ( ABC News: Clarissa Thorpe )

"When the children are able to … they can actually be largely responsible and not cause some of these issues that have occurred in the past," he said.

"They will grow up doing all the other areas that we've asked them to do in the march, and when they reach the age when their parents or the organisations feel that they're capable, they will take their place in carrying placards and flags and other things within the march."

It is another controversial decision by the RSL after community bands were cut from performing at the march.