BRITAIN's biggest-ever warship will have to be partially repainted amid fears she may rust.

In the latest hitch to hit the Royal Navy's £6.2bn aircraft carrier programme, contaminants have got in to some of the topcoat on the giant HMS Queen Elizabeth.

Engineers building the 65,000-tonne giant believe this happened as they rushed to get the carrier ready for its launch last year.

Sources said dust and particles from grinding and hot work got in to the paint as it was applied.

A source close to the project said: "This will cause rust to form as it corrodes in salt water conditions."

HMS Queen Elizabeth was launched just over a year ago and is currently being fitted out at Babcock Marine's yard in Rosyth Fife.

She had to be painted before leaving her dry dock in what was a massive operation. The ship is 920ft long and her paint, insiders stress, is vital to ensuring she completes a predicted 50-year lifespan.

HMS Elizabeth - and her sister ship HMS Prince of Wales - are being built until the £6.2bn programme by a consortium of BAE Systems, Thales and Babcock Marine.

A spokesman for the consortium, called the Aircraft Carrier Alliance, said engineers were confident the painting problems would not hold up work currently under way.

He said: "During routine quality inspections, we identified an issue with a small part of the topcoat applied to the hull of HMS Queen Elizabeth.

"This affects one per cent of the hull and we have a plan to reapply the paint in these areas without any impact on the programme."

Sources were unable to say how much the repainting would cost. Even a small section of the a hull the size of HMS Elizabeth's is huge. However, they said that work could be carried out while on-going efforts are made to fit out the vessel continued.

Crucially, official sources stressed that the problems were on the side of the hull, above the water line. That means the ship can be repainted without taking it back in to dry dock.

Engineers are currently powering up the ship with its own generators as they instal different parts of its complex systems.

The ship is not due to sail to her home port of Portsmouth in southern England until 2017 and will not be fully commissioned until 2020. HMS Prince of Wales will follow two years later.

The entire project has been controversial, not least since it emerged the ship will initially not have any fixed-wing aircraft.

The 2010 strategic defence review ruled that Britain should only have one carrier, not two. However, get-out clauses meant that it would wasteful not to complete the second ship. Last year David Cameron confirmed that HMS Prince of Wales would be commissioned y the Royal Navy rather than mothballed or sold.

The two carriers have guaranteed some 4,000 jobs in Scotland and any hitch can look bad for manufacturers. BAE Systems, currently preparing to make frigates on the Clyde, has already downsized its Portsmouth yard after a corvette order for Trinidad and Tobago was cancelled after cost overruns and delays. That cost the company £100m.