The protocols - called Questions of Procedure for Ministers - do not at present refer to union payments. This has effectively barred ministers from making public pronouncements on disputes involving trade unions because of the money paid out to individual constituency Labour parties.
At present, the Cabinet Office rules state: "Ministers should take care to ensure that they do not become associated with non-public organisations whose objectives may in any degree conflict with government policy and thus give rise to a conflict of interest."
The rules have already presented problems. Glenda Jackson, the junior transport minister whose Hampstead and Highgate constituency received pounds 2,000 last year from Aslef, the train drivers' union, should, under these rules, refrain from commenting on the dispute between Connex South Central and its Aslef employees.
But a spokesman for Ms Jackson's office denied that she had been silenced adding that "there was no conflict of interest".
To date, Ms Jackson has not issued a statement regarding the strike - which affects thousands of commuters in the South-east. The Cabinet Office, however, does recognise the problem. "This issue does need to be resolved and will be accounted for through the current revision," said a spokeswoman.