Transport Minister Keith Brown said he would oppose proposals to divert the overnight trains from Euston, in north London, to Waterloo, south of the Thames, when work starts on HS2 in two years.
He said such a move could affect the overnight train service, the franchise for which will be up next year.
It is feared such a switch would increase journey times and the cost of running the service.
The issue comes as the boss of HS2 today proposes speeding up of the building of the northern, phase two, section of the £50 billion project.
HS2 Ltd chairman Sir David Higgins also called for a larger development at Euston - the project's southern terminus. In a report entitled HS2 Plus, Sir David said reducing the contingencies which have pushed the total cost of the project up would be "irresponsible".
But he said cost cuts might be possible later and he laid down the gauntlet to politicians by saying the speedier the HS2 legislation the better for cost reductions.
Mr Brown said: "We are aware of Department for Transport proposals for HS2 works that would see Caledonian Sleeper services unable to access Euston station in the run-up to HS2 phase one opening in 2024 and we entirely reject these plans.
"Speculation of this type creates uncertainty and is unhelpful at this late stage of the refranchising of this service. We will not allow this last-minute change at DfT to derail our own well-run franchise processes."
He added: "The Caledonian Sleeper is an iconic service, valued by passengers and of vital importance to Scotland, and we will not accept any solution which adversely impacts on passenger experience or the future viability of the service."
Sir David, the former London Olympics supremo, said HS2 was "vital for the future of the country".
He added: "Without HS2, the people of this country will continue to face the failures of our transport system on a daily basis."
A Department for Transport spokesman said: "We are confident we will be able to continue London to Scotland sleeper services during the building works at Euston."