The former Prime Minister, Tony Blair, will appear before the Iraq inquiry commission on January 29 to answer questions about his controversial decision to support the Iraq invasion, especially the allegation that he misled Parliament and the country by distorting intelligence about the “threat” from Saddam Hussein to justify the invasion.

Mr. Blair is expected to face some uncomfortable questions over claims that he committed Britain’s support to the U.S.-led invasion months before a formal decision was taken.

Alastair Campbell, who was his chief of communications at the time, told the inquiry last week that he assured the then U.S. President George W. Bush in 2002 that he would support any military attack on Iraq if diplomatic efforts to “disarm” Saddam Hussein failed.

The assurance was given in private letters that Mr. Blair wrote to Mr. Bush.

“Yes, that was the tenor,” said Mr. Campbell when asked if he was aware that Mr. Blair gave such an assurance.

Mr. Campbell’s remarks confirmed that Mr. Blair and Mr. Bush had agreed on a military solution while in public they were claiming that no decision had been taken.

Sir Christopher Meyer, then British Ambassador to Washington, said in his evidence Mr. Blair appeared to have made up his mind about regime change in Iraq after a private meeting with Mr. Bush at his Crawford ranch in early 2002.

It has emerged that Jack Straw, who was Foreign Secretary, warned Mr. Blair in a “secret and personal” letter in March 2002 — one full year before the invasion — that any military attack would be illegal.

Mr. Blair is the most high-profile figure to appear before the five-member inquiry, chaired by Sir John Chilcot, retired senior civil servant. It is looking into Britain’s role in the Iraq invasion and the “lessons” to be learned from that military adventure.

Prime Minister Gordon Brown will appear after the general election expected in May.