Five former Northern Ireland secretaries have written to The Times warning that a hard border “threatens the very existence” of the Good Friday agreement

David Davis has blamed the lack of progress on finding a solution for the Irish border on a “change of government in Dublin” and accused the Irish government of allowing Sinn Féin to influence its hardline stance on Brexit.

In inflammatory comments to a conference in London, the Brexit secretary said Leo Varadkar had allowed Republican sentiment to play “a strong political role” in Brexit that had made it harder to resolve the border impasse.

His claims were dismissed last night by the Irish government, but risk heightening tensions between the two administrations in the midst of talks aimed at resolving the border issue.

It comes as five former Northern Ireland secretaries write to The Times today to warn that a hard border “could threaten