Scottish Power's chief operating officer, Keith Anderson, told UK national newspaper the Daily Telegraph the project was being scaled back because government subsidies were insufficient.
Anderson said if the project failed to receive government support all together, then it could be cancelled.
The 1.2GW East Anglia One project - part of a larger 7.2GW East Anglia Zone - is being developed by a joint venture between Iberdrola-subsidiary Scottish Power and Swedish utility Vattenfall.
It could be the second time Scottish Power Renewables has cancelled a major offshore project, after dropping the 1.8GW Argyll Array in December 2013.
When contacted by Windpower Monthly, Scottish Power refused to comment on the rest of the 7.2GW East Anglia development zone.
Some in the UK industry believe it is possible that other developers will scale back the size of their projects unless the way the government allocates Contracts for Difference (CfD) changes.
The UK government's new CfD subsidy scheme has a £235 million (EUR 300 million) yearly budget to support less established technology projects, like offshore wind. But this is expected to support only up to 800MW of new projects - including other technologies in the 'less-established' pot.
Anderson said the East Anglia One project could be reduced in size so that its subsidy need is within the CfD budget.
East Anglia One could join a number of large UK projects which have been cancelled in the last year:
- In November, RWE stopped developing the 1.2GW Atlantic Array due to "signifcant technical challenges".
- Scottish Power's 1.8GW Argyll Array was cancelled in December. Scottish Power Renewables said technical difficulties specific to the site, off the east coast of Scotland, were to blame for the decision.
- In July, Centrica announced its exit from the offshore sector. This cancelled its agreement with Dong Energy to develop the 4.2GW Irish Sea Zone. Centrica said challenging seabed conditions made the project economically unviable.
- Earlier in October, RWE also decided against going ahead with the 340MW Galloper project. The company cited tight time scales to secure financing while still qualifying for the soon-to-expire renewables obligation subsidy scheme.