The Ministry of Defence is to buy a new £200m C-17 military transporter to move troops around and help with any future Libya-style evacuations, David Cameron announced on Wednesday.

The prime minister told MPs the coalition had found savings at the MoD that would allow it to purchase the additional Boeing-built aircraft for the RAF.

The announcement came as the cross-party defence select committee warned today that Britain could struggle to mount an operation on the scale of the Libya mission in the future.

Challenged about the committee's report in the Commons, Cameron said: "Because the Ministry of Defence's finances are better run and better managed, and because we have found savings, we will be able to purchase an additional C-17 for the RAF.

"This aircraft is becoming an absolutely brilliant workhorse for the RAF in terms of bringing men and material into a war zone like Afghanistan, but also evacuating civilians in times of need.

"It's an important investment for the country and I'm glad to announce we can make it today."