It follows train operator Serco apologising for repeated failures after travellers highlighted “filthy” and litter-strewn rooms aboard the £150 million fleet.
It is understood that Leadec, which cleans the carriages on behalf of train maintenance firm Alstom, will be replaced by Servest.
Sources said staff were not properly supervised to ensure cabins were left clean and tidy on the trains, which were introduced on the Glasgow and Edinburgh to London routes in April.
The carriages, which feature cabins with ensuite showers and toilets, are due to enter service on the remaining routes between Aberdeen, Fort William, Inverness and London by next month.
Serco admitted “standards we set for room presentation were not met” after The Scotsman revealed the problem last month.
Fergus McCallum, who travels on the sleeper weekly, said he had found berths in a “disgusting” state on two journeys within days of each other.
The pharmaceuticals consultant from Pitlochry said the room was “filthy, bins not emptied, hair on the toilet bowl, toilet roll pieces on the floor... used ear plugs on the bed, children’s sweet wrappers and jewellery, and, as every time, hair on the pillows and beds.
“They are absolutely not cleaning the beds between customers – it’s filthy.”
He welcomed the action taken to improve things.
Mr McCallum said: “I think it’s good Serco is facing up to the situation and is taking robust steps to manage the problem. I spoke to the customer experience manager last week and he genuinely seemed to listen.
“I told him my honest opinion as someone who uses the service every week that for the last few months they have been simply straightening the bedclothes and not changing them.
“I told him I travel with a sleeping bag so I don’t have to touch the sheets.
“He seemed genuinely shocked and I believe he intended to fix this situation.”
An Alstom spokesman said; “Alstom is proud of the maintenance work we do to keep the Caledonian Sleeper running but we are always looking to improve the service we deliver for our customers.
“We recognise there have been some issues recently, and as part of our ongoing efforts to improve services I can confirm we are looking at options for better cleaning of these specific trains in the future.”
Ryan Flaherty, Serco managing director of the Caledonian Sleeper, said: “Bringing our new trains into service has been very complex and challenging and we have been working closely with all our partners to resolve the issues we have faced.”
A Leadec spokesman said: “We have been working very hard with each party to resolve the issues faced during the launch of the new Caledonian Sleeper trains and to maintain the standards and expectations of both the client and passengers.
“The Caledonian Sleeper contract was due to expire as part of the normal, periodic competitive retendering process.
“Leadec was one of several companies taking part, and the decision to source the contract was taken on a commercial basis.
“We are, of course, disappointed, but we remain a committed and active service provider to the transport sector.”
Serco has also suffered technical problems with the trains which have led to breakdowns in the middle of the night.
A London-Edinburgh service had to be halted with an emergency brake after running through Waverley Station.