Any involvement of the IRA with Colombian terrorists is unacceptable, the prime minister has said.

Tony Blair told the Commons at question time on Wednesday that evidence of IRA involvement with FARC rebels was a "serious issue".

"That is why we are making it quite clear to Sinn Fein and any paramilitary organisations that such behaviour is unacceptable," he said.

Three Irish republicans are awaiting trial in Colombia on charges of training FARC rebels.

Three Irishmen await trial in Colombia

But Mr Blair urged Tories to reflect upon opposing "every single stage" of the government's work in Northern Ireland.

"I ask them to reflect a little bit on how much the last five years have brought Northern Ireland and how totally irresponsible it would be if we broke the bipartisanship that we offered them on this issue."

Action call

Earlier Conservative MP Graham Brady said there was "overwhelming evidence" of IRA involvement with the promotion of terrorism in Colombia.

"What action do you propose to take against the IRA as part of your war against terrorism?" he asked the prime minister.

Mr Blair said Labour had not criticised the last government when it emerged they were in secret talks with Sinn Fein and the IRA.

"I would have hoped that the same responsibility that characterised our relations with them when they were in office would have characterised theirs with us but I afraid I am disappointed."

Mr Blair's comments come just a few days after the adviser to President Bush on Northern Ireland warned that any new evidence of IRA involvement in Colombia would have "extremely serious consequences".

Richard Haass: Zero tolerance for terrorism

Richard Haass said there was growing evidence that the IRA had been involved in training FARC rebels in the recent past.

In an interview for the BBC News 24 Hardtalk programme, Mr Haass said the US government had zero tolerance for connections to international terrorism.

"There is clearly a pattern there that things that the FARC are now doing are things that they did not do previously," he said.

"I am told by weapons experts, of which I am not, that many of these things bear certain patterns or hallmarks of IRA operations.

"There is a prima facie, or an apparent case, that clearly there was training that went on that made a difference."