McKevitt told Dublin's Special Criminal Court he had been forced to sack his barristers following two failed attempts to have the hearing halted. 

Three judges had rejected an attempt by the defence to stop the trial on the grounds that their case had been irreparably damaged due to the non-disclosure of crucial surveillance documents they claimed could have cleared the accused. 

But after all his legal representatives walked out of the courtroom McKevitt, aged 53, said: "I will not participate any further in this political show trial and am now withdrawing myself with my dignity intact." 

Defence lawyers had claimed surveillance papers which they were not told about until after the trial began could have provided an alibi for McKevitt, from Blackrock, Dundalk, Co Louth. 

He denies directing the Real IRA and being a member of the terror organisation which killed 29 people in the 1998 Omagh bomb atrocity. 

The evidence threw into confusion part of the testimony from star prosecution witness FBI agent David Rupert about attending a meeting of the dissident republican army council in February, 2000. 

The judges rejected two separate attempts to halt the trial, ruling that the issue could be dealt with by recalling Mr Rupert to the stand.

As the drama mounted, McKevitt read out a statement outlining the reasons for dispensing with his barristers' services. "In his statement, Mr Rupert alleged I attended an army council meeting on February 17, 2000. However, recently disclosed Garda surveillance situated me in my home on that date. Why was this withheld for two-and-a-half-years?" 

The accused also claimed his solicitors wrote to State prosecutors 12 months ago requesting access to all relevant surveillance documents. 

In October last year detectives wrote back stressing that all outstanding material was either irrelevant or being withheld on the grounds of national security, he said. However, recent disclosure had, according to McKevitt, "rendered worthless the assurances" of the Garda. 

McKevitt accused military intelligence of deliberate interference in order to strengthen Mr Rupert's credibility and also claimed detectives told him his arrest had been "a political order from on high'. "The discrepancies between certain MI5 documents which refer to his (Mr Rupert's) criminal past and his evidence before this court is simply beyond belief." 

Even though he did not want to dismiss his legal team, the accused insisted the decision had been forced upon him