MPs have criticised the Government for an "unacceptable" refusal to reveal the full costs of F-35 warplanes.
The Commons Defence Committee said the Ministry of Defence (MoD) refused repeated requests to provide the full cost of each F-35 Joint Strike Fighter once spares, upgrades and retrofits are included.
Along with a failure to provide estimates of the total cost of the programme beyond 2026/7, this risks "undermining public confidence" in plans to order 138 of the stealth fighters, it said.
The UK is currently embarked on a £9.1 billion programme by 2025 to purchase 48 of the F-35s, the world's most advanced fighter jet, from American aviation giant Lockheed Martin.
Britain currently has 13 of the jets in the United States being tested ahead of flight trials off HMS Queen Elizabeth next year - but has pledged to purchase 138.
Defence Committee chairman Julian Lewis said: "There has been an unacceptable lack of transparency from the MoD and Lockheed Martin which risks undermining public confidence in the programme.
"F-35 is a major investment for the UK and we want it to succeed for the good of this country's security.
"However, it is precisely because this project is so important that it must be subjected to the closest possible scrutiny."
The committee warned that the failure to provide adequate cost estimates was "wholly unsatisfactory".
It said the MoD must publish "rough orders of magnitude" it has for the total costs of the programme beyond 2026/7.
Its inquiry into the F-35 programme was launched after a Times investigation reported claims that the jet was "way over budget, unreliable, full of software glitches and potentially unsafe".
The report said the broadband capacity of the Queen Elizabeth carrier will need to be boosted beyond the reported eight megabits, and will likely have to exceed the 32 megabits available on the USS America, if the full benefits of the F-35 are to be realised.
The MPs called on the MoD to provide them with six-monthly updates on the programme including details of the ongoing costs.
The MoD said it would be "simply irresponsible" to publish in-house estimates of the future costs of the F-35 programme beyond 2026, because the purchases of the aircraft are subject to negotiation and so revealing estimates would undermine the Government's position.
A spokesman added: "We strongly refute any suggestion of a lack of transparency in the F-35 programme, which has been subject to intense scrutiny not only from this inquiry, but from the UK's independent public spending watchdog and in our regularly published reports.
"As ministers, civil servants and members of our Armed Forces have emphasised, the programme remains on track, on time, within costs and not only offers our military the world's most advanced fighter jet but will support over 24,000 British jobs and is very much clear for take-off."
The MoD also insisted the broadband bandwidth on Queen Elizabeth class aircraft carriers is sufficient to "carry out the scope of carrier strike operations", but stressed it was not constrained by design and could grow.