Despite its popular image of vastness the Titanic was no bigger than a modern North Sea ferry, an expert in marine technology has said.

The doomed liner was the largest ship afloat when completed in 1912, but a gas processing vessel to be finished in 2016 will be six and a half times its size and some giant cruise ships are almost five times bigger.

Paul Stott, a senior lecturer at Newcastle University's School of Marine Science and Technology, raised the issue because it has a relevance to another, more recent disaster, the loss of the Costa Concordia off the coast of Italy two years ago.

Reports of the ongoing salvage operation frequently refer to the vessel being around twice as large of the Titanic, he said in the Mariner's Mirror journal.

Even if any living person had seen the Titanic, the comparison fails as it would not be particularly big in the modern context, Mr Stott explained.

''Whilst large in her day, Titanic would be equivalent only to a mid-sized ferry in the modern era, the sort of ship many have sailed on to get to France or Holland, and this normally comes as a revelation,'' he said.

''Stating that the Costa Concordia is around twice the size of the Titanic gives a vague impression that they were trying to move a large object, but not in any tangible way that can give a direct sense of the scale because none of us have actually seen Titanic.''

It would be more meaningful to use famous buildings as a comparison, he argued - with the Costa Concordia being around twice the size of St Paul's Cathedral or equivalent to the Gherkin in London.