A parliamentary inquiry has been ordered into the government's decision to approve the first commercial planting of GM crops in the UK.
Legal responsiblity for any cross-contamination will be looked at
The Commons environment committee is to investigate the implications of the move to allow the growing of one variety of GM maize for animal feed.
The MPs are to look at the risk of cross-contamination, and if it occurs, who will be legally responsible.
The planting decision has incensed anti-GM campaigners.
Environment Secretary Margaret Beckett announced on Tuesday that ministers had agreed in principle to the growing of a single variety of GM maize in England.
She told MPs the government would oppose the growing anywhere in the European Union of beet and oilseed rape - the two other GM crops involved in recent tests, known as the farm-scale evaluations.
She said the GM maize licences would expire in October 2006, and any consent holders wishing to renew them would have to carry out scientific analysis during cultivation.
Her approach was "precautionary" and "evidence-based", she said.
There was "no scientific case for a blanket approval for all uses of GM... and no scientific case for a blanket ban on the use of GM".
Any commercial crops would have to be grown and managed as in the tests, or under conditions which would not harm the environment.
But Greenpeace said it was incensed the government had chosen to ignore British public opinion.
"Who on earth is Tony Blair listening to? He's given the nod to GM maize based on trials that anybody with a passing knowledge of A-level science would be able to tell you were flawed," said campaigner Sarah North.
As part of its inquiry, the environment committee will also look at the processes involved in determining how GM-free zones will be established at regional and local levels, and what role the government should play in this development.
Interested parties will be required to submit written evidence by Monday, 19 April.