The referendum on the proposal to abolish the Seanad will involve some 40 changes to the Constitution, the chairwoman of the Referendum Commission has said.

At the launch of the Commission's €3.3 million information campaign on the two referendums that will be held on October 4th, Ms Justice Elizabeth Dunne said that many of the changes would be "simple deletions".

She said the most significant are described in the Commission’s independent guide which was also published today.

She also disclosed the commission had used focus groups to assist its preparations of its guide and its campaign - this initiative, she said, was possible because the Commission has had a longer run-in period than in previous referendums.

Next month’s referendums will ask people to decide whether to abolish the Seanad and whether or not a new Court of Appeal should be established.

The guide sets out the facts in relation to the referendum and explains what situation will arise should the referendum be passed.

It sets out the 14 major changes that will occur if the Seanad is abolished. All but one will involve either a transfer of powers to the Dáil or the Dáil assuming sole responsibility in a matter.

This includes the passage of legislation through the Oireachtas. According to the guide, the power that currently resides in the Seanad to delay the passage of a non-money Bill by 90 days will no longer be applicable with a unicameral (single-chamber) House.

One explicit Constitutional power that will be discontinued is a provision whereby a Bill can be referred to the people for a referendum if a majority of Seanad members, and more than a third of Dáil members, ask the President not to do so. The grounds for the petition must be that it contains a proposal of such national importance that the decision to have such a law should be made by the people. The President can accept or reject the request.

The guide states: “If this referendum is passed, the possibility of the reference to Bills to the people by the President will be removed from the Constitution.”

All five members of the Commission were at the launch. They were Ms Justice Dunne: the Ombudsman Emily O'Reilly; retiring Clerk of the Dáil Kieran Coughlan; Clerk of the Seanad Deirdre Lane; and the Comptroller and Auditor General Séamus McCarthy.

Ms Justice Dunne said the Commission had a budget of €3.3 million but would be unlikely to spend all of its funds over the next month.

Its campaign would involve all forms of media, including social media such as twitter and facebook and reminded people that part of its remit was to encourage voter turn-out.

Referring to social media, she said: “If we target young people that way, great. If we target older people that way, even better.”

At the launch of the campaign Ms Dunne said the referendums involved “very straightforward questions”.

Asked if the commission should have set out the context of the referendum, including the history of why Ireland had had a second chamber - as well as the employment of unicameral and bicameral systems in other jurisdictions - Ms Dunne said on those questions one "could fill volumes that would take up the entire space of the room. The reasons are multifactored and multivarious".

Ms Justice Dunne said there was very little uniformity in relation to this issue and it was not simply about looking at other countries in the EU.

She said a document had been prepared by the Houses of the Oireachtas Commission on the countries that do and do not have two chambers.

Explaining why it was not included in the booklet, she said: “There are so many pieces of information that it would be distracting from a straightforward proposal.”

She said the Commission wanted to give information in a “pithy and reasonable” fashion. She said if all of the legislative changes had been included, it would have been very tedious for anybody to have read through that.

The section on the establishment of the Court of Appeal outlines the Constitutional change to allow the legislature set up a new court level between the High Court and the Supreme Court.

A Court of Criminal Appeal already exists on the criminal side to hear appeals on criminal cases from the High Court, the Circuit Court and the Special Criminal Court.

The booklet has stated there are long delays in appeals to the Supreme Court being heard and says if the referendum is passed the new court will hear virtually all appeals from of High Court decisions.

It has also outlined the other major change contained in the referendum, a change in a rule in relation to Supreme Court rulings on whether or not a law is constitutional.

At present the decision is given by one judge out of the minimum of five Supreme Court Judges who make the ruling.

It is not then known if there was any disagreement with the decision. If the referendum is passed, it will allow all five judges give his or her opinion in public.