Mr McNamara has written to Sir Patrick Mayhew, the Secretary of State for Northern Ireland, asking him to use his prerogative to have the cases re-examined by the Court of Appeal.
The Labour spokesman questioned whether the convictions were safe and said public unease about many aspects of the trials was growing.
The cases arose from the murders of two Royal Signals corporals, Derek Wood and David Howes, who drove into a republican funeral in west Belfast in March 1988. The soldiers were dragged from their car, stripped, beaten and finally shot dead on waste ground.
Since then more than 40 men have been prosecuted in eight major trials, the most recent of which was held in Belfast last month. Concern about some aspects of the trials has been expressed by a number of human rights organisations, including Amnesty International and the Belfast-based Committee on the Administration of Justice.
Mr McNamara's action will lend further momentum to a campaign which has received increasing attention over the past year. His weekend call centred on the three cases which have attracted most attention, those of the Belfast men Michael Timmons, Patrick Kane and Sean Kelly.
They received life sentences for aiding and abetting the soldiers' murder. They were allegedly present for several minutes at an early stage of the incident, before the soldiers were driven away and shot elsewhere.
In last month's trial, charges against five defendants were dropped, a sixth was found not guilty and the seventh received a suspended sentence. The proceedings were attended by observers from Amnesty, the CAJ and the Haldane Society of socialist lawyers.
The prosecutions amounted to one of the most intensive police and legal operations ever mounted in the United Kingdom, with a large team of detectives and very substantial resources devoted to the inquiry.
The outcomes varied considerably, with five men jailed for life and others imprisoned for terms of up to nine years, though more than half the defendants have been acquitted or received non- custodial sentences.
Mr McNamara said the judge who found Kane, Timmons and Kelly guilty had not paid enough attention to a preceding incident in which three people at a republican funeral were shot dead by a loyalist gunman. He wrote: 'The judges in these trials seem to have taken an extremely inconsistent approach to the surrounding circumstances within which the killing of the corporals took place.
'The atmosphere on the day, according to several of those present, was tense, angry and despairing. In these three cases the judge was, in my view, unreasonably dismissive of the chaos, confusion and hysteria following the blundering upon the funeral cortege of corporals Howe and Wood.'
Mr McNamara said he also had major concerns about the use of film of the incidents taken from an Army helicopter, the use of anonymous witnesses and other matters.