Whitehall sources last week confirmed that Lord Justice Scott's inquiry is now likely to be published in the autumn.
Ministers sent copies of passages criticising and detailing their activities have taken longer than expected to respond and have slowed the process.
Although Lord Justice Scott still hopes to report in July, one source said large sections remain unwritten and publication will probably be delayed. So Mr Major must decide whether to go ahead with a quick reshuffle, then risk destruction of his new line-up, or appear to be running scared of the report's findings.
Doubts about the timing of Scott's inquiry came as Tory MPs yesterday played down claims of a split between John Major and his Secretary of State for Defence, Malcolm Rifkind, over devolution. Yesterday Mr Rifkind reiterated his sympathy for the principle of devolution, while arguing that there was no practical method of achieving it within the Union.
On Friday Mr Major told the Scottish Conservative Party Conference that devolution was a "stepping stone" to independence.
In a fractious Radio 4 Today interview, Mr Rifkind yesterday said he wished there was some way that the desire for a separate Scottish parliament could be reconciled with maintaining the Union.
He said: "To be perfectly honest, I wish I could see such a way because I am well aware that certainly in Scotland, perhaps in Wales, there are many people who have an enthusiasm for some greater degree of local decision- making but also want to remain British."
Meanwhile the Scottish Nationalists have an 11 point lead over Labour in the Perth and Kinross by-election with the Tories trailing in third place, according to an opinion poll by telemarketing researchers Proctor and Proctor, for GMTV's Sunday Programme.