The UK needs to be 'very, very careful' in developing a policy on GM crops post-Brexit, NFU vice-president Guy Smith told the co-operative United Oilseed's harvest review.Farming minister George Eustice said last month that Brexit gave the UK an opportunity to grow GM crops. "The Government’s general view remains that policy and regulation in this area should be science-based and proportionate," he said.Guy Smith said the issue of what should and should not be grown has to be left to science not the market but said: "I am very conscious that everything I grow on my farm has to have a market, I have to grow what consumers want to eat, I have to be very mindful of markets."If the UK takes a pro-GM attitude, where are our exports going to go? If we start to develop a different policy to the rest of the EU, those issues will raise their heads and we need to be very, very careful."VanguardHSBC head of food and agriculture Allan Wilkinson said GM technology as 'old science' and the UK needed to be at the vanguard of new science, 'which is already underway elsewhere.'"But we need to make sure it's safe and consumers want it. This is about leading from where the consumer comes from and that will give us unfettered access to new ways of thinking and doing things, provided consumers want them."Mr Smith said the future after the Brexit vote wasn't clear."The best crystal balls are showing a very fuzzy picture both in the UK and the EU. It’s not clear in the Tory party who has the upper hand – those who want a hard or soft Brexit."ContaminationDespite rapid adoption by farmers in many countries, controversies about the technology remain. Even Pope Francis has criticised the use of GM technology in the past. Greenpeace, Friends of the Earth, GeneWatch UK, GM Freeze and the Soil Association each expressed concerns that controversial Roundup Ready GM crops might be planted in England in Spring 2015. They said that would eventually harm the environment.""Monsanto and other GM companies are desperate to push their GM crops into other countries before the devastating impacts on wildlife and farming destroy existing markets," said Dr Helen Wallace, Director of GeneWatch UK. The Government should not be caving in to commercial lobbying and putting British birds and butterflies at risk."