Labor MPs accused of rorting taxpayer funds in the "red shirts" affair have refused to be interviewed by fraud squad detectives.

Prominent lawyer Rob Stary, who is representing about 20 members of the Andrews government including six ministers, is understood to have informed police last week that his clients would not be attending formal interviews.

The refusal to co-operate with the police request has caused frustration among some officers involved in the investigation, who must now make a decision on laying charges without the opportunity to question the MPs or hear their accounts.

Premier Daniel Andrews flanked by Gavin Jennings and Martin Pakula. Credit:The Age

Police have the power to arrest the MPs, who would have the right to give a "no comment" interview once they had been advised of their rights.