After decades of generous subsidies from Brussels, some British farmers are starting to think the unthinkable – that they might be better off outside the EU. Farmers were strong supporters of membership when Britons last voted on it in 1975 and they flourished for years as funds flowed into the sector to encourage ever-rising production.

But with Prime Minister David Cameron preparing to call an referendum on Britain's membership of the bloc as early as June, some farmers feel the benefits of belonging to the Brussels club are far less compelling than a generation ago. Robert Law, who farms 4,000 acres of arable land at Thrift Farm in Hertfordshire, says red tape and EU directives have stifled British farming.

"When we joined Europe, we went into a free trade area. There were just nine members. Now there's 27. The EU is trying to make one size fit all," he said. The EU consists of 28 Member States.

Law breeds more than 2,500 sheep and blames the EU for oppressive bureaucracy and crippling paperwork. "When I came into farming, I spent 95% of my time out on the farm working. Now I spend 95% of my time administrating and far too many hours of the night, hours of the day attending to administration in the office," he said.

British farmers receive £3bn ($4.4bn) a year in support payments from the EU, which makes up about 55% of total income from farming, according to government figures.

"Every farmer would admit that yes they do help us, but they come at a big price of a lot of regulation and because we're all in this system, we're all receiving payments. It is sort of built into our financial return. It's all part of the system now," said Law.

George Chichester, a partner at Strutt and Parker, an estate agent which has 100 years of experience in farm management, says that if Britain lost subsidies from Europe, the government would have to make up the shortfall.

"If we come out of Europe, then the subsidy support would have to come from the UK government. Then we have to compete with the many demands from the UK purse, at a time when we have massive public sector debt and private debt as well", he said.

"There are many other serious contenders for that money too, if there is money available for the taking. So we have to compete against the education budget, the national health budget, the military budget, the police budget and whatever it may be," he added.

While full-time farmers are relatively few in number – only 140,000 in 2014, according to government figures – they wield considerable influence in rural communities which, come election time, vote overwhelmingly for Cameron's governing Conservatives. Not all are swayed by the argument that leaving the EU would make life easier. Some worry that subsidies could be cut and they might lose access to important European markets if Britain breaks with Brussels and its Common Agricultural Policy (CAP).

The Kendall family has owned Church Farm in Bedfordshire for more than 150 years. Former president of the National Union of Farmers Peter Kendall farms more than 800 hectares of land with his brother,. He says that the EU is a long-term commitment and gives farmers confidence. Kendall added that he does not believe that a Brexit would lead to less bureaucracy.

"When people say to me there will be less regulation, I just don't see it and certainly talking to Norwegian farmers, they know they meet every single one of those regulations that the EU imposes because they need access to that market of 550 million people," he said, adding that British farmers are much safer as part of a bigger club that looks out for agricultural interests.

"When you are in a long-term business, confidence is everything. I hear from those who want to leave EU making lots of promises about what they might give to us as farmers, but actually being part of the European Union, 28 member states who think long term, probably for many of those countries agriculture is more important than it is to the UK, so being part of a club that thinks long term, that is very much behind agriculture as an industry, gives me more reassurances as a farmer to plan for our future," Kendal said.

The outlook for UK farming outside the EU could hinge on what access is granted to key export markets and the extent to which Britain is prepared to maintain support payments. Britain's exports of wheat, for example, are dominated by EU destinations, with Spain and the Netherlands the most important customers in recent years. Leave campaigners argue that Britain will be able to negotiate better trade deals from outside the bloc.

Cameron attends a vital summit with European partners in Brussels on 18-19 February. He hopes to renegotiate reforms to Britain's membership ahead of a referendum on EU membership which could take place later this year.