McGuigan is president of the Professional Boxers' Association whose members say they are 'stunned' that Watson is still having to wait for a pay-out from the British Boxing Board of Control.
The PBA has written to the BBBC calling for an extraordinary general meeting 'to clarify doubt and confusion regarding the financial and administrative affairs of the body supposedly in charge of professional boxing in Britain'.
PBA officials, including McGuigan, the chairman Nicky Piper and the secretary Colin McMillan, are 'bewildered by the increases in expenses and charges'. They are 'concerned about inadequate provision for insurance cover for boxers and stunned that the financial reserves of the BBBC, which amount to pounds 414,905, have not been used to assist Michael Watson'.
Watson suffered near-fatal brain injuries in a World Boxing Organisation super-middleweight title fight against Chris Eubank at Tottenham in September 1991 and was in a coma for 40 days.
The top pay-out under the terms of the Board's insurance policy is normally pounds 20,000.
John Morris, the BBBC general secretary, has said: 'It's a matter that is being exclusively dealt with by our solicitors because we want to get the best possible deal under the limits of the policy.'
However, the PBA asked: 'Why can't the board make an advance payment to Michael and await the outcome of the insurance study?'
Darren Fifield's attempt on the European flyweight title ended in a points defeat by the Italian, Luigi Camputaro, in Bristol last night.