Field trials of a genetically modified crop containing fish oil nutrients in its seeds could begin in the UK this year.

Scientists hope to produce the world's first sustainable plant source of fish oil omega-3 fatty acids by "cutting and pasting" genes derived from marine algae.

Initially the aim is to benefit the fish farming industry, which consumes 80% of fish oil supplies.

But in 10 years time, the GM-produced oil could be finding its way into food products such as margarine.

An application to conduct the trials at Rothamsted Research agricultural institute has just been submitted to the Department for Environment, Food and Rural Affairs (Defra).

Assuming all the regulatory hurdles are crossed, the first crop could be sown in around three months time.

The plant, Camelina sativa - or "false flax" - is widely cultivated in Europe and North America as a source of vegetable oil, animal feed and biofuel.

Scientists chose it for the research because it already contains high levels of plant fatty acids and its genes are easy to manipulate.

By substituting synthetic versions of up to seven genes from marine algae, the researchers have engineered Camelina plants to produce two key omega-3 fatty acids normally obtained from oily fish, EPA and DHA.

Both are said to have important health benefits, including protection against heart disease.

"We now have a vegetable oil enhanced with these two critical fish oils," said lead researcher Professor Johnathan Napier, whose team based in Harpenden, Hertfordshire, has worked on the project for 15 years.

"The next really exciting challenge for us is to say, 'We know it works in the glasshouse; does it work in the real world?'

"We have applied to Defra for permission to carry out a field trial."

Plants such as flax and linseed contain omega-3 fatty acids, but they are not the same as the long-chain compounds in fish oil.

Oily fish such as tuna, mackerel, and sardines do not produce long-chain omega-3 fatty acids naturally either.

They only obtain them by consuming certain types of marine algae.

In this way, the molecules move up the food chain.

The economics of fish farming mean that, rather than feeding on algae, farmed fish have to be given their omega-3 in the form of fish oil.

Enormous quantities of fish oil are taken up by the aquaculture industry, amounting to 80% of available supplies.

With farmed fish accounting for half current fish consumption there are concerns about providing enough marine omega-3 to maintain the industry and meet human demand.

GM plants such as Camelina have the potential to make fish farming more sustainable and ease the pressure on wild fish populations, the scientists believe.

Prof Napier doubted omega-3 supplements would be a "natural market" for fish oil nutrients produced from GM plants.

But he did envisage the fatty acids being incorporated into food products such as margarine.

"By the end of this decade, there's a possibility that people will be able to obtain a GM plant-based source of fish oils," he said.

Despite past controversy surrounding field trials of GM crops, the team does not expect its work to meet strong opposition.

"If you have a crop that's got the potential health benefits and sustainability and environmental benefits, and we can articulate that clearly, then I think people will see this is an OK thing to do," Prof Napier said.

"It's not a controversial thing to do.

"The technology is not particularly controversial."

A hectare of GM Camelina would be expected to generate just under a tonne of vegetable oil - about 80% of the yield level of oil seed rape.

Tests show that about a quarter of the oil consists of long-chain omega-3 fatty acids, 14% DHA and 12% EPA.