Northern Ireland First Minister Peter Robinson has threatened to resign if Justice Minister David Ford allows prison reform that could remove royal insignia and titles from jails.

He made clear he would take the ultimate political step of quitting the job and trigger an election if the symbolic change was enforced.

Mr Robinson told party colleagues that the Queen's insignia would not be removed, adding: "Not on my watch."

Mr Robinson said: "It will not happen on my watch, let's make this very clear."

He added that any change in British emblems was out of the question, and said: "It is simply not on the agenda."

The Democratic Unionist Party leader said that if Mr Ford tied the proposed changes in symbolism to his reform programme, than the entire process could be compromised.

The Justice Minister is involved in implementing a major overhaul of the prison system, which evolved during the years of violence, and which a string of damning reports have said is unfit for the needs of the 21st century.

Last week Mr Ford unveiled a £60m redundancy package to allow prison officers who served during the Troubles to leave the service, so new staff could be recruited.

The Justice Minister said the reform package had to include an enhanced exit scheme to recognise the service of prison staff - with 29 members murdered during the Troubles.

The redundancy scheme is only one element of wide reform which will see a major shake-up of all facets of the prison regime.

At the time the redundancy scheme was announced, officials said a reform of the service's symbols and emblems - such as uniform or badges - may also be necessary to secure cross-community involvement in a service whose uniformed officers are predominantly Protestant males.

Prison officer ranks include nearly 1,800 staff, with around 80% drawn from the Protestant community, 10% from the Catholic community and 10% of non-denominational background.

But Mr Ford has already said he would oppose a 50/50 recruitment scheme for Protestants and Catholics such as the one that was used over the last decade to reshape the police service in Northern Ireland.