Enda Kenny's warned that border checks with Northern Ireland are inevitable if a so-called 'Brexit' goes ahead.
The Taoiseach says that while a common travel area will remain, border controls would be unavoidable for customs reasons:
He made the comments as he announced plans to visit Britain next week to speak to Irish communities ahead of the referendum - in a tour that will take in Liverpool, Manchester and Glasgow.
Next Friday he will share a stage with British prime minister David Cameron at an Irish community centre in Manchester.
He says Ireland has made it clear what outcome it wants - but it won't try to lecture British voters:
