The air force's new stealth jet is on track and on budget, the defence minister said today.

A £250m refurb is under way from RAF Marham, which will be the home of the F35 Lightning from next summer.

But earlier this week, reports from a US government watchdog said it was beset with problems, which would push up the cost of the £100m aircraft.

In a letter to South West Norfolk Elizabeth Truss MP, the Defence Minister Harriett Baldwin said: 'The programme is on track. Today there are over 100 British pilots and aircrew training in the US on our 10 F-35s before they arrive in the UK next year.

'Those best placed to comment on the F35 capability are those who have flown them as part of 95,000 hours of test flights.'

Wing Commander Jim Beck, one of the UK's most experienced F-35 pilots, said: 'The F-35 is the best aircraft I've ever flown. It is the most advanced multi-role fighter jet out there and the aircraft most suited to the UK's needs.

'With huge flexibility and cutting-edge innovation, this supersonic, stealth aircraft will bring about a generation change in the way we fight in the combat air arena for many decades to come.'

By the end of this year the RAF will have 14 F-35 aircraft and in 2018 flight trials will begin from the HMS Queen Elizabeth, building towards delivering a UK carrier strike capability from 2020.

The minsiter said as well as providing first rate military capability, UK-based companies benefit from 15pc of the value of the manufacture of every F-35 on what is the largest global defence programme ever. Last year the UK was chosen to be a global repair hub for hundreds of European-based F35s, supporting thousands of high skilled jobs.

Elizabeth Truss said: 'The multi million pound investment taking place at RAF Marham in preparation for the arrival of the F35 in 2018 is fantastic news for Norfolk. The build programme at the base is well underway with many local contractors benefitting from the substantial upgrade that is taking place. Marham will be part of the largest global defence programme ever and this translates to significant job opportunities, providing a boost for skills and training as well as the massive economic benefits that this all brings to South West Norfolk.'