Norwegian classification society Det Norske Veritas, in its latest research estimates that 492 vessels, or 37.2m dwt, have been removed from the orderbook.
This figure includes 325 bulk carriers of around 28.2m dwt, 78 containerships and 47 tankers of 4.9m dwt.
The new estimates are nearly double those of rival classification society Lloyd's Register, which cites figures showing confirmed cancellations totalling 2.3% of the orderbook. France's Bureau Veritas confirmed that 40 newbuidings it was classifying have been cancelled.
The uncertainty over how many ships will be built reflects the lack of concrete information from yards in the world's two largest shipbuilding countries, South Korea and China, as well as their strategies to deal with owners who cannot raise the money to pay for a glut of ships on order.
Yards are reluctant to detail cancellations, but at least several major shipbuilders in China have accessed funds via government-backed banks to build and own cancelled bulk carriers, which will be begin trading by the year's end.
"This is an indirect subsidisation effectively," said Diana Shipping president Anastassis Margaronis. "It's not the way we saw [subsidisation] in the 1980s, but through the credit door or the finance door.
They're not reducing the price of the construction of ships by giving grants but they are facilitating the building of the ships by offering credit and debt to the yards."
Shipping executives who have recently visited yards in China, where half the world's bulk carriers are on order, reported that yards were keen to build ships, and open to requests for delivery deferrals, also offering to renegotiate prices based on any cost savings.
Bulk carriers comprise about 53% of the 556.5m dwt, or 8,950 ships ordered, nearly 70% of the existing fleet's capacity. These newbuildings are set for delivery at a time of lower-than-expected growth in seaborne demand for bulk commodities.
Mr Margaronis said Diana Shipping estimated that 22% of these bulk carriers would be cancelled in 2010 and 2011, based on research from London brokers Howe Robinson and Clarksons.
This would see a further 282 bulk carriers cancelled in 2010 and another 306 in 2011, based on "ballpark figures" that divided the average size of bulk carriers order by the total dwt.
Mr Margaronis said it was "extremely difficult" to build an accurate picture about the future bulk carrier fleet. "We present our company as potential purchasers of cancelled tonnage and yards are very reluctant to accept that some tonnage has definitely been cancelled, as it's definitely there to be sold, we are talking to four separate shipyards about tonnage which appears to be there for sale."
The legal position of yards was also uncertain, as they did not have clean title on vessels, even when the owner had defaulted on pre-delivery payments, Mr Margaronis said.
So far handymax bulkers of 40,000 dwt-59,999 dwt account for 35% of the dry bulk newbuilding contracts cancelled. Suezmax tankers accounted for the largest number of tanker cancellations, with 10 vessels dropped, DNV said. South Korean shipyards saw 194 ships cancelled. There were 161, or 12.9m dwt, cancelled at Chinese yards.
DNV has forecast that 30% of bulk carrier and container orders, and 10% of tanker newbuldings will not be built.
"To do a cancellation is quite costly and the big yards are saying no," said DNV senior vice-president Wilhelm Magelssen.
"We have a surplus of tonnage whether we like it or not. This would still have been the case without the financial crisis."