The Treasury is refusing to publish a forecast of the UK's economic outlook alongside this Friday's mini-Budget.
Independent forecaster the Office for Budget Responsibility (OBR) has already provided a draft to Chancellor Kwasi Kwarteng, the BBC understands.
The Treasury Select Committee says a forecast is "vital" given recent UK Government moves to curb living costs.
Action on energy bills for households and firms could cost more than £100billion, and tax cuts are also anticipated on Friday.
The mini-Budget is expected to see the government reverse a rise in National Insurance and scrap a planned increase in Corporation Tax, which reports say could cost £30billion.
It has also been reported today that Prime Minister Liz Truss and Mr Kwarteng have been working on radical plans to cut Stamp Duty south of the border, in an attempt to drive economic growth. More details are expected in the mini-Budget.
The draft forecast which the OBR has provided to the chancellor does not include the impact of the energy bills help. It has offered to provide a forecast including this impact, but that has been rejected.
'Flying blind'
The fact the offer has not been taken up is raising some concerns about whether the government's tax and spending policy is "flying blind", given predictions that the UK is facing a lengthy recession.
MPs on the Treasury Select Committee wrote to the chancellor on Tuesday seeking assurance that an OBR forecast would be published.
"These forecasts are a vital indicator of the health of the nation's finances, and provide reassurance and confidence to international markets and investors," said the committee's chairman, Mel Stride.
"There has been a deterioration in our economic outlook since the last OBR forecast in March. There have been significant fiscal interventions since then and we are told there will be further significant interventions including major permanent tax cuts to be announced on Friday.
"Under these circumstances, it is vital that an independent OBR forecast is provided."
The OBR is obliged to produce economic forecasts twice a year, usually accompanying the Autumn Budget and Spring Statement.
A spokesperson for the Treasury said: "Given the exceptional circumstances our country faces, we have moved at immense speed to provide significant energy bill support for households and businesses, and are acting swiftly to set out further plans to kick-start economic growth later this week.
Remain committed
"We remain committed to maintaining the usual two forecasts in this fiscal year, as is required."
Mr Truss has been in the US for a meeting with President Joe Biden. She told the BBC last night that she is prepared to take "difficult decisions" such as removing a cap on bankers' bonuses to boost the economy.
The PM said that spurring economic growth may mean doing unpopular things. Her government is considering removing a cap on bankers' bonuses as part of a post-Brexit shake-up of City rules.