Lord Tebbit: Martin McGuinness needs to confess crimes
The former Conservative minister, Lord Tebbit, has said Martin McGuinness should confess his crimes before standing for the Irish presidency.
"Those who were responsible for atrocities should own up to that and confess what they have done," said Lord Tebbit.
"In order to seek the forgiveness of those whom they had damaged."
Sinn Fein will formally announce its intentions for the Irish presidential election later.
It announced on Friday that it would be supporting Martin McGuinness for the role.
This is expected to be ratified by Sinn Fein's Ard Chomhairle on Sunday
Mr McGuinness has secured the necessary support of independent members of the Irish parliament for his nomination.
They are Finian McGrath, Luke Flanagan, Michael Healy-Rae and Tom Fleming.
On Saturday, the deputy first minister said he was prepared to meet all heads of state "without exception", if he is elected President of Ireland.
When the Queen made her first visit to Ireland in May, Sinn Fein did not take part in any of the main ceremonies.
He said: "If the people of Ireland decide that I should be their president, my responsibilities and duties would be to meet heads of state from all over the world and to do that without exception and that would be my position."
A former IRA commander, Mr McGuinness has been deputy first minister since 2007.
While he is likely to face significant scrutiny of his paramilitary past, his party colleagues believe his high profile during the peace process should help build the Sinn Fein vote.
Earlier this year, the party won 14 seats in the Irish parliament, Dail Eireann - its strongest performance in the modern era.
Fine Gael's Gay Mitchell, Special Olympics boss Mary Davis, businessman Sean Gallagher and Labour's Michael D Higgins of Labour, have already put their names forward for the October election.