A Labour frontbencher has said he is "deeply sorry" for claiming the Good Friday Agreement and the Irish border issue were being "played up" for economic reasons during the Brexit talks.
Barry Gardiner, the shadow international trade secretary, described the historic peace deal as a "shibboleth" - a Hebrew term for a custom or belief distinguishing a particular group of people, often one that is considered as outdated - and played down fears that a hard border would reignite paramilitary activity on the island of Ireland at an event in Brussels last month.
However after his remarks prompted criticism, Mr Gardiner issued a statement saying he "absolutely" did not believe the agreement was outdated or unimportant.
The threat of a hard border after Brexit has proved to be a key sticking point in the talks, as negotiators struggle to find a way to curb the threat of violence and the need for regulations between the EU and the UK.
Mr Gardiner's comments emerged as leading political figures were due to gather in Belfast to mark the 20th anniversary of the 1998 agreement, which helped to bring an end to The Troubles in Northern Ireland.
It also came as senior political figures spoke out over the risks of a hard border of the island of Ireland, with former US secretary of state Hillary Clinton declaring the "hand of history will be both heavy and unforgiving" if Brexit was allowed to undermine the peace process.
Mr Gardiner, a close ally of Jeremy Corbyn, originally said reports of his comments were "nonsense on stilts".
But a recording now emerged of his remarks, where the former Northern Ireland minister said: “We must also recognise that there are real economic reasons why people have played up the issue of the Irish border and the need to have the shibboleth of the Good Friday agreement.
"And that is because it is hugely in the Republic of Ireland’s economic interest to make sure that there is no tariff and no external border there.
“And of course there are very good political reasons. Sinn Fein, who are members of this group and trusted colleagues, of course want to see the unification of Ireland and that is a political objective of Sinn Fein.
"But it doesn't mean that a normal border will bring back paramilitary activity."
He later issued a statement, saying the Good Friday Agreement was "a vital and essential part" of the relationship between the UK and the Republic of Ireland that has been "central to the two decades of peace".
"Labour is completely committed to the agreement and opposed to any return of a hard border between North and South," he said.
"We are committed to negotiating a new customs union between the UK and Ireland as part of a final Brexit settlement, which would play a key role in ensuring there is no hard border.
"I am deeply sorry that my informal remarks in a meeting last month have led to misunderstanding on that point - in particular, that my use of the word 'shibboleth' in its sense of 'pass word' or 'test of membership' gave the impression that I thought the Good Friday Agreement was in any way outdated or unimportant. I absolutely do not."
Former shadow Northern Ireland secretary Owen Smith, who was sacked for urging the party to stay in the single market, attacked his Labour colleague for the remarks, which he described as "both reckless and plain wrong".
Mr Smith said: "I worked in Northern Ireland with Barry and it is remarkable that he can display so little understanding of the vital and continuing importance of the Good Friday Agreement, or of the essential need to avoid any hardening of the border in Ireland.
“Labour members will be particularly shocked, but it should concern people in every party and none that there now seems to be a substantial group of senior politicians – from Daniel Hannan to Barry Gardiner – who are prepared to sacrifice the Good Friday Agreement in order to deliver Brexit.”
Ex-Prime Minister Tony Blair, who played a key role in securing the deal, said it was "not a shibboleth, it was absolutely fundamental to keeping the peace" in Northern Ireland.
He told BBC Radio 4's Today programme: "I don't know how anybody could say that. It's the only basis on which you could have peace."
Meanwhile, five former Northern Ireland secretaries have penned a sternly-worded letter warning against a hard border, which they said could "threaten the very existence" of the peace deal.
In a joint letter to The Times, organised by the pro-Europe group Open Britain, Lord Mandelson, Lord Reid, Lord Hain, Lord Murphy and Shaun Woodward said: "We are concerned that the re-introduction of a hard border will lead to instability that could threaten the very existence of the agreement.
"Those who value the agreement and the peace it brought to Northern Ireland have a duty to speak up and make clear their opposition to the Government's Brexit policy. They should insist that the option of continuing in the customs union and single market remains open."
But former Taoiseach Bertie Ahern said Dublin could have to "play hard ball" with Britain over Brexit, as he insisted that any return to a physical border would be unacceptable.
He told Newsnight: "There never will be a border. There is not going to be a physical border across Ireland because if you tried to put it there you wouldn't have to wait for terrorism to take it down, people would just physically pull it down - the ordinary people."
Former US president Bill Clinton, Mr Blair and former Irish Taoiseach Bertie Ahern will be among those marking the 20th anniversary of the landmark deal at Queen's University in Belfast on Tuesday.
The agreement, which included the release of hundreds of political prisoners, was codified by the British and Irish governments, with the backing of most Northern Irish parties, except for the Democratic Unionist Party.
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