Hunting has become a "touchstone" for wider issues
Campaigners staged a string of protests across the country at other Defra offices.
They claim the rural way of life is under attack from a remote, metropolitan government.
'Authoritarianism'
Admiral Sir James Eberle, of the Association of Masters of Harriers and Beagles, told supporters in Smith Square: "We are here in a fight - and I fought in three wars and know a bit about it."
He said hunting was only part of the issue and they were in "a fight for the whole countryside."
He said there was "a touch of the sort of authoritarianism" in the government's attitude which brought back memories of 1930s Europe.
'Foolish to ignore'
Countryside Alliance chief executive Richard Burge has urged members to take part in "law-abiding but determined protests" against rural affairs ministers at their official engagements.
In an open letter to the government, letter, he warned: "It would be foolish to ignore the scale and depth of distrust and anger rural people feel at this moment.
"Politically, the countryside is tinder-dry.
"Hunting has become the touchstone for the countryside's overall concerns.
"Rural people have lost faith that the institution of government will deliver a fair and just resolution to this problem."
Consultation
The protest follows last month's hunting votes in the Commons and Lords.
The government has said it will consult for six months before going ahead with new legislation on the issue.
'Noisy minority'
Commenting on Friday's protests, Shadow Environment Secretary Peter Ainsworth said: "This urban Government doesn't seem to understand the problems facing the countryside and is widely believed not to care."
But a spokesman for the League Against Cruel Sports said: "This clearly shows that the Hunting Alliance is resorting to more and more desperate tactics because they have already lost the argument.
"They are a small and noisy minority of people who do not properly reflect the views of rural people."
London march
The Smith Square delegation included members of the Countryside Alliance and the Council of Hunting Associations.
Defra offices in York, Carlisle, Nottingham, Chelmsford, Bury St Edmunds, Gloucester, Exeter, Carmarthen, Whittington, Reading, Reigate, Worcester, Stafford, Caernarvon, and Newcastle saw similar presentations and rallies.
The Countryside Alliance claims 500,000 country people will march on central London before Parliament rises for the summer in July to show the rage felt those whose jobs and livelihoods would be threatened by a ban on the sport.
Its last large-scale march in 1998 attracted 250,000 supporters.
The alliance is talking to the Metropolitan Police about a possible date for the London march.
A date has not been fixed, but a spokesman told BBC News Online it would be before parliament's summer recess.