The Taoiseach is to meet new British prime minister Keir Starmer in Downing Street later this month.
Simon Harris spoke with Mr Starmer on Friday evening and warmly congratulated him on his appointment.
Both men spoke of their shared determination to reset and strengthen the bilateral relationship between Ireland and the UK and to set about that task with urgency and ambition.
Mr Starmer invited Mr Harris to meet him in Downing Street on July 17, and the Taoiseach accepted.
They discussed Northern Ireland, welcoming the restoration of the institutions, including the full operation of north-south and east-west Good Friday Agreement institutions, as well as legacy issues.
The Taoiseach also welcomed the appointment of Hilary Benn as Secretary of State for Northern Ireland.
Both men agreed a closer relationship between Dublin and London was needed and a meaningful reset would require regular engagement between them.
They agreed to start work on that immediately and to stay in close contact.