Former Prime Minister Tony Blair engaged in a "deliberate deception by omission" by failing to tell the majority of politicians in Northern Ireland about the agreement his government struck with Sinn Fein to deal with on-the-run republicans, Stormont's First Minister has said.

Peter Robinson heavily criticised the conduct of the previous Labour administration as he addressed an emergency meeting at Stormont to debate the controversy over letters sent to more than 180 terror suspects informing them the authorities in the UK were not seeking them. Democratic Unionist leader Mr Robinson said his predecessor Ian Paisley had written to Mr Blair when he was in power asking for assurances no concessions had been given to Sinn Fein about on-the-runs (OTRs).

He said the reply stated there were no plans to legislate on the issue, and no amnesty had been offered but, Mr Robinson said, it did not make mention of the administrative scheme to send OTRs assurance letters.

"The answer that there were no plans to legislate and no amnesty would be introduced was a deliberate deception, a deception by omission, for the Government could easily at that stage have indicated there was an administrative process which included giving letters to OTRs was under way," he told MLAs (Members of the Legislative Assembly).

The recalled Assembly convened shortly after another Stormont minister claimed applications for five on-the-run republicans for assurance letters were still being considered by the current government.

Democratic Unionist Economy Minister Arlene Foster yesterday went further and challenged the UK Government to immediately stop consideration of the cases involving on-the-run IRA terror suspects who have asked for assurances they are not wanted by police.

Addressing a full chamber at the conclusion of the ill-tempered and rancorous debate at Parliament Buildings, Mrs Foster first directed a pointed message to Sinn Fein. "They have always had a cavalier attitude to the rule of law, but they need not underestimate our continuing determination to rebuild confidence and that must start with the five cases we have learnt of this morning."

Mrs Foster delivered a stark ultimatum to the Northern Ireland Office (NIO) regarding the cases. "They must immediately go, they have to be stopped immediately - I think that will be a mark of how this issue goes forward and we will be asking that question of the Secretary of State [Theresa Villiers] very quickly.

"I make it very clear from this House that we are not just dealing with the past, as we have learnt this morning, we are also dealing with the here and now in relation to this system."

Asked about the five cases, the NIO said it would not be commenting in detail on the OTRs scheme due to the forthcoming judge-led review of the system, which was announced by Prime Minister David Cameron yesterday.

The five cases were brought to light by Stormont Justice Minister who said he had been informed of their existence by a "senior NIO official". Details of 180-plus letters sent to OTRs emerged when the case against a man charged with the 1982 IRA Hyde Park bombing collapsed. John Downey, 62, from Donegal, denied murdering four soldiers in the attack in London.

The case ended because government officials mistakenly sent him one of the assurance letters in 2007 telling him he was no longer a wanted man. But the collapse shone light on the wider policy of sending such letters to on-the-runs, with many politicians in Northern Ireland claiming the scheme was operating without their knowledge.