Defence manufacturers have urged David Cameron to clear up "confusion" over how the replacement of Britain's nuclear deterrent would be funded.
Uncertainty about whether the successor to Trident would impact on wider defence spending was causing "great concern" and "unsettling" investors, trade organisation ADS warned.
The industry body appealed to the Prime Minister after Defence Secretary Liam Fox clashed with Chancellor George Osborne about whether the Ministry of Defence would foot the £20 billion bill.
Dr Fox has warned that having to cover the cost from the MoD budget would impact on other defence capabilities. Mr Osborne has repeatedly insisted that the bill would fall to the MoD.
In a letter to Mr Cameron, ADS chairman Ian Godden said the UK-based defence industry had "reflected with great concern on the recent statements by senior ministers in the media about the nation's nuclear deterrent".
Private investors were looking for "real clarity" about the Government's defence priorities from its Strategic Defence and Security Review (SDSR), he said.
But the ministers' comments appeared to "throw doubt on the Government's full commitment to the deterrent" and suggested that "its costs will fall on MoD potentially at the expense of other expenditure".
Industry needed to know whether replacing Trident would lead to extra cuts in the requirements of the Armed Forces, he said.
"The uncertainty caused by these statements will be as unsettling for investors as it must surely be for our allies," Mr Godden wrote.
"A decision to move Trident renewal to the defence budget without a commensurate transfer of funding calls into question the integrity of the SDSR process and complicates the future funding of our conventional capabilities and our nation's ability to support its allies. It is vital that this confusion is cleared up as soon as possible."
