People arriving at the Tory party conference in Manchester were subjected to abusive chants as ugly scenes followed a largely peaceful march involving tens of thousands of protesters.
MPs, party members, journalists, lobbyists and staff at the conference centre were called "scum" as they ran the gauntlet of demonstrators outside the Manchester Central venue.
Police made four arrests after an estimated 60,000 people took part in a demonstration in protest at Government policies as the conference opened.
Chief Superintendent John O'Hare of Greater Manchester Police said: "Today around 60,000 people took part in a demonstration and I would like to thank them for their cooperation.
"The overwhelming majority of people have exercised their democratic right to protest with dignity and good grace.
"The fact that only four arrests have been made throughout the day so far was particularly pleasing."
Although the majority of protesters were well behaved, a series of journalists complained of being spat at while one conference-goer was hit by an egg.
A growing crowd of anti-Tory demonstrators gathered around the security gates into the conference, shouting "Tory scum" and "murderers" as people walked in.
Dozens of police officers, some on horseback, were seeking to prevent any physical confrontations between the groups outside the Midland Hotel.
A protester was arrested after Huffington Post journalist Owen Bennett was spat at, with TUC general secretary Frances O'Grady labelling the behaviour "inexcusable".
Jeremy Corbyn, who is breaking with convention for an Opposition leader tomorrow by speaking at a protest meeting happening alongside the conference, has appealed to those taking part to keep it peaceful.
Union leaders and officials from campaign groups including CND addressed a rally in the city centre before leading the procession.
Singer Billy Bragg warmed up the growing crowd with a set on stage, changing the lyrics to his best-known songs to add topical references such as "take the money from Trident and spend it on the NHS" and "these Tory cuts will get me the sack".
The rally began in bright sunshine - with many holding banners from the country's biggest trade union Unite.
A variety of slogans featured on mass-produced and home-made placards, including Cut War Not Welfare, Don't Bomb Syria, No Cuts and Divine Discontent, Divine Disobedience.
Several costumes and banners featured images of pigs, poking fun at Prime Minister David Cameron over allegations made in a controversial biography about a bizarre student ritual.
Unite general secretary Len McCluskey told the rally the protest was "sending a very clear message to this Tory Government" that they faced a fightback.
"If they think a fluke victory in which 75% of the electorate did not vote for them gave them a mandate to continue their cuts then they've got another thing coming.
"If they think they are going to have a smooth ride over the next five years, they've got another thing coming.
"There will be hundreds of thousands of people hounding them, snapping at them and resisting them."
The fight would be easier because in Mr Corbyn, Labour has a leader "who will stand shoulder to shoulder with us", he said.
Ms O'Grady said restrictions in the Trade Union Bill were "the biggest attack on the democratic organisation of working people for 30 years".
"This is about attacking our right to strike. And we say no way."
Conservatives attending the conference have been advised by the party not to display their accreditation outside the secure area around the Manchester Central venue in case they come under attack.