Northern Ireland Secretary James Brokenshire has rounded on Jeremy Corbyn for his "IRA sympathies".
Mr Brokenshire accused the Labour leader and his party colleagues, shadow chancellor John McDonnell and shadow home secretary Diane Abbott, of having "extremely worrying views" about IRA terrorism.
Mr Corbyn has come under fire for refusing to single out the IRA for condemnation when pressed over his past campaigning activities during a television interview on Sunday.
The Labour leader said "all bombing is wrong", as he was repeatedly asked to condemn the IRA alone for its role in the Troubles.
He said he had worked hard to help secure peace in Northern Ireland.
But Mr Brokenshire - who prior to the calling of the General Election had been facilitating talks between Stormont's Sinn Fein and the Democratic Unionist Party in a bid to restore powersharing - demanded Mr Corbyn and his top team "come clean about their true attitudes towards IRA terrorism".
He accused Mr Corbyn of having a "long political career of sympathy for the IRA cause".
"I have listened with interest and concern to the various attempts by Jeremy Corbyn and John McDonnell to explain their attitudes towards IRA terrorism during the 1980s and 1990s.
"Their complete failure unequivocally to condemn terrorism, and to attempt to contextualise it, are deeply worrying coming from two people who in just over two weeks seek to be entrusted with the security of the United Kingdom," said Mr Brokenshire.
He said the Labour leader and his top team need to make clear if they believe the IRA were terrorists, if their activities should be condemned and if they regarded members of the Armed Forces and the IRA as "equivalent" participants during the Troubles.
Mr Corbyn's campaigning during the Troubles has come under renewed scrutiny since his election as Labour Party leader.
He and shadow chancellor John McDonnell have been prominent supporters of Sinn Fein.
Before the IRA ceasefire, they controversially met the party on a number of occasions in Westminster during the 1990s.
The Labour leader has said the meetings formed part of his attempt to bring about peace in Northern Ireland at that time.
He has also been criticised over his activities with the Troops Out movement, which campaigned to end British military involvement in Northern Ireland in the 1980s.