Martin McGuinness, the former IRA commander who is now deputy first minister of Northern Ireland, has sharply criticised David Cameron’s lack of engagement with the peace process and accused his government of making a series of “stupid and unhelpful” decisions that have hurt supporters of peace.

“People may be shocked to discover that Peter Robinson and myself have met American President Barack Obama more times that we have met [the UK prime minister] in our role as first and deputy first ministers,” said Mr McGuinness on Thursday.

In a speech on British-Irish relations delivered a day after his historic handshake with the Queen, Mr McGuinness attacked Mr Cameron’s handling of the peace process.

“The lack of engagement by David Cameron is a serious mistake and may provide a rationale for some of the damaging decisions made by Owen Paterson during his tenure at the Northern Ireland Office,” he said.

Mr McGuinness said these included the revocation of the licence and imprisonment of Old Bailey bomber Marian Price and the failure to hold inquiries into the murder of human rights lawyer Pat Finucane and the killing of 11 civilians by the British army in August 1971, an event known as the Ballymurphy massacre.

“Unfortunately to date the British state has refused to even acknowledge its role as a combatant in the conflict. That position is no longer tenable as we move forward. It is insulting to victims of events like Bloody Sunday in my own city when 14 people were killed and it is insulting to people’s intelligence,” he said.

Mr McGuinness said it was a mistake to think the peace process had ended with the success of the devolved assembly. He said the task of building national reconciliation was as much a part of the peace process as anything that had gone before.

“I genuinely regret every single life that was lost during the conflict and today I want every family who has lost a loved one to know that your pain is not being ignored and I am willing to work with others to finding a way to deal with our past so that we can complete our journey to true reconciliation,” he said.

He said this was the context for his meeting with the Queen.

“I was in a very pointed, deliberate and symbolic way offering the hand of friendship to unionists through the person of Queen Elizabeth for [whom] many unionists have a deep affinity.”

Mr McGuinness called on the British people and MPs to become persuaders for constitutional change to bring about a united Ireland.

“Britain’s involvement in Irish affairs has been marked by colonialism, plantation, division and partition. It has been bad for Ireland and her people and bad for Britain and her people,” he said.

He said the partition of Ireland was an “outdated relic of the past” and a “symbol of political failure” and called for a fresh approach to British-Irish relations.

“That will not happen if the British government continues to cling to old certainties born from a different era and a different time,” he said.

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