Protesters plunged a stake through a horse's heart before dumping its carcass outside Brighton Station today.

Around its neck was a placard reading: "There will be more of this if you ban hunting."

A dead cow and two calves were also dumped in the shadow of the fountain in Steine Gardens.

Countryside Alliance banners reading "59 per cent of the public say keep hunting" were placed beside their decomposing bodies.

The Alliance immediately distanced itself from the sickening discoveries, believed to be the actions of a militant wing of the pro-hunting campaign.

The carcasses were discovered half an hour before more than 2,000 demonstrators marched on the Brighton Centre, where Tony Blair was making a speech appealing for his party to unite.

The blare of hunting horns mingled with the shrill of whistles and cries of "no ban" as supporters chanted their slogans accompanied by the barking of hounds.

But the noisy protest was overshadowed by the shocking mafia-style dead animals protest in the busiest parts of the city.

The two areas were taped off by police and guarded by park wardens before the carcasses were removed.

Officers shielded their faces from the overwhelming stench of rotting flesh as flies circled.

One witness said the cattle had been dumped in Old Steine at around 11.25am, when two farmers accompanied by a television crew unloaded them from a van.

Jason Abrahams, who works at the Frank-in-Steine cafe, said: "It is not only disgusting. It is a health hazard.

"Children run around here all day. If that's their mentality, to bring that sort of thing to Brighton, I hope they put a full ban on hunting."

Another eyewitness added: "They arrived in an old van and dragged the animals out, leaving them on a path in front of a fountain.

"They looked like farmers and I think the men were quickly arrested by police.

"It's terrible for the people around here and must be a risk to public health. I hope they don't carry on acting like this because it won't win them any friends or help their argument."

Lee Hughes, an IT manager at Lloyds TSB in Queens Road, said: "The horse was tied to a lamppost outside the Royal Standard pub.

"This was a cheap way of getting publicity."

Tourist Edna Chilton, from Stoke-on-Trent, said: "It is a disgusting thing to see on holiday. It is not what you expect in sunny Brighton. It's so over the top. Someone must have seen them putting them there in broad daylight."

A spokeswoman for the Countryside Alliance said: "We have been informed of what has happened, but we do not believe this has any connection to our organisation.

"We cannot explain why our banners were left at the scene."

Peter Setterfield, from the South East Countryside Alliance, said: "I think it's appalling."

David Winnick, Labour MP for Walsall North who has been one of the most vocal supporters of a ban on hunting, condemned the action.

He said: "This is absolutely disgusting. It seems quite clear that this kind of stunt is being used instead of reasoned argument by the hunting lobby.

"What they have done today will simply put even more people off from supporting hunting with dogs.

"I say to those responsible, you should be thoroughly ashamed of yourselves. You have brought even further discredit on your cause."

Two men were arrested in the city centre.

They were being questioned by police and could face charges under regulations relating to the disposal of dead animals.

Coun Simon Burgess said: "I share the outrage of most of the people in the city. If the protestors think this is a way of gaining support they have clearly lost the plot. It's going to upset people and I'm just glad my children didn't see it.

"I'm just sickened by it. The council will be establishing cause of death and hope to bring a prosecution if possible."

Meanwhile, Mr Blair was today urging Labour to unite behind a radical third term agenda as he bids to heal party wounds over Iraq.

Mr Blair was expected to use his address to say that while mistakes could have been made in the run up to the war in Iraq he will not apologise for ousting Saddam Hussein from power.

The premier was also expected to praise Chancellor Gordon Brown's stewardship of the economy, saying that it remains the foundation for all his party wants to achieve.

That will be seen as an olive branch to Mr Brown's supporters, who now seem to have conceded that the Chancellor will never take over in Number 10 before the next election.

The Prime Minister was tryimg to switch the focus back on to health, education, transport and help for "hard working families".

That will involve pledges for extra assistance with childcare, a guarantee of further training for all workers who wish it, and a new drive to improve secondary education.

Yesterday, Mr Brown urged Labour to use his record on managing the economy as the springboard for a successful General Election campaign.

In his keynote speech, the Chancellor told the party's conference that in seeking to persuade voters that they can trust the Government in the post-Iraq conflict era, activists can still cite his economic record.

And he insisted that the party and country should give Prime Minister Tony Blair their full support in the "difficult times" generated by the Iraqi conflict.

In what some commentators viewed as a dig at Alan Milburn - to whom Mr Blair has handed Mr Brown's traditional role in masterminding Labour's election campaign --the Chancellor spoke of his ambition to build a "progressive consensus" on Britain's future which amounted to "much more than a set of individual policies announced by politicians".

Shadow chancellor Oliver Letwin predicted that a third term for Labour would see council tax double and National Insurance contributions soar by £900 a year.

He told the BBC Radio 4 Today programme: "We have now got significant deficits and that means we are going to have third term tax rises if Labour is re-elected.

"The question people have to ask themselves is do they really want to have a council tax which goes from £1,000 for a Band D property to £2,000? Do they really want to see a £900 increase in National Insurance contributions?

"If they want not to see those things, and I think most of our fellow-countrymen don't, we have to thin down the fat bureaucracy Mr Brown has created and we have to do something to get this country out of this horror of increased taxes."