Mr Varadkar also criticised large corporations for not paying their fair share of tax
The Taoiseach has told the European Parliament that Europe has reached a decisive point in its history.
Leo Varadkar was in Strasbourg this morning, addressing MEPs on the future of Europe.
In his speech, Mr Varadkar said it is hard to imagine the Good Friday Agreement being made without Ireland's membership of the EU.
He offered his thanks for the “remarkable solidarity and support” he said Europe had shown towards Ireland during the first phase of Brexit talks.
Noting that the success of the Good Friday Agreement can largely be traced to Ireland's membership of the EU, he said the Irish people are “profoundly grateful for the unswerving support of this Parliament.”
He made it clear however, that the commitments made in the Brexit negotiations so far need to be upheld:
“The breakthrough achieved before Christmas means that the United Kingdom has guaranteed that, whatever its future relationship with the European Union, a hard border on the island of Ireland will be avoided,” he said.
“The Common Travel Area and its associated rights will be maintained.
“As the negotiations move forward, into Phase Two, we will continue to rely on your support and solidarity as we work to ensure that what has been promised in theory is delivered in practice.
“There can be no backsliding on this.”
He said it is essential that the commitments made thus far are included in the legal text of the Withdrawal Agreement, and firmly embedded in the future relationship between the UK and the EU, “whatever shape that ultimately takes.”
“For my part, I hope that it will be as close and deep as possible and consistent with the need for the Union to protect our internal market and the Customs Union,” he said.
British MEP Nigel Farage however had some choice words for the Taoiseach on Brexit.
He accused Mt Varadkar of being a “European Unionist” and insisted he was working with Tony Blair and Nick Clegg to get a second referendum:
“You are part of course of a big attempt here and elsewhere to frustrate and to attempt to overturn Brexit,” he said.
“You don’t want Britain to leave because you know if they do, others will leave too.”
The Taoiseach is the first European leader to outline his vision for the future of Europe in a series of planned debates.
He used the opportunity to hit out at large corporation for not paying their fair share of tax – but insisted that his “strong view” was that “national taxes that fund national budgets should be determined by national parliaments and governments.”
Equally strong is my view that corporations should pay their fair share of tax. We cannot tolerate a situation where large companies can avoid paying any taxes anywhere.
That is as true for American tech companies as it is true for European car manufacturers and for international aerospace and defence companies.
He insisted Ireland had “already taken steps to close loopholes” in its tax laws and pledged to do more.
“We strongly believe this should be done on an international basis through the OECD,” he said.
“Europe should not give advantages to our competitors by acting unilaterally.”
He said the Apple case was a State aid case rather than a tax case adding that the European Court of Justice would judge on it.
"Ireland is not a tax haven, we don't want to be a tax haven and we don't want to be seen or perceived as a tax haven,” he said.
Mr Varadkar is due to attend a number of high-level meetings on Brexit. This afternoon
The engagements include meetings with the President of the European Parliament, Antonio Tajani and with the European Parliament’s Chief Brexit Coordinator, Guy Verhofstadt