Relations between British and Irish ministers could suffer if the UK leaves the EU, a former Taoiseach has warned.

Bertie Ahern said the chemistry between partners could change if the European connection and side meetings in Brussels were lost.

He warned Northern Ireland could be particularly affected.

"We are all practical people, most people in here are business people. Politicians are the same, half the time the business is done on the side.

"The letters are flying back and forwards and the memos are flying and emails but it is that side business where you can go to a colleague at a European meeting and say listen, there is something going on, can you help do anything, on almost a personal basis.

"There is a huge benefit when that happens in Northern Ireland between British ministers and Irish ministers every week of the year and Europe would lose that if we were to split."

Mr Ahern and Tony Blair brokered the 1998 Good Friday Agreement in Belfast which largely ended violence in Northern Ireland.

It followed years of intensive talks between unionists, nationalists and governments in Belfast, London, Dublin and Washington.

Mr Ahern addressed a Newry conference on Britain's referendum on Europe.

"There is a huge amount of meetings in a European context and it does help chemistry between politicians and so therefore if that European connection went it would not change the policy but it would change the human relationship and that would be a worry.

"Those human relationships, Albert Reynolds had it with John Major, I had it with Tony Blair, it continues on with the ministers now, that is very important and where I would have concern."