Labour MP Jim Murphy has suspended his Scotland-wide referendum tour, claiming that Yes Scotland is employing intimidation tactics by co-ordinating mobs of protesters to disrupt the meetings.

The suspension comes after Mr Murphy was heckled by Yes supporters and hit by an egg in Kirkcaldy, Fife, yesterday during his 100 Towns in 100 Days tour for Better Together.

The Labour MP has been making his case for the union by getting on his soapbox - two Irn-Bru crates - in towns across Scotland since June, but he said the past fortnight had seen events take a "sinister turn for the worse".

The tour has been suspended for 72 hours to seek guidance on safety from police, and to give Yes Scotland "time to call off this mentality", Mr Murphy said.

Police Scotland are already investigating the incident in Kirkcaldy.

Mr Murphy said he had also been challenged to fights, and labelled a "terrorist", "quisling" and "defender of paedophiles", while staff had been abused for being English or Northern Irish.

He said: "This tour is intended as a way of getting out and about on Scotland's high streets to debate the referendum with undecided voters, and the first 70 meetings were great - passionate people on both sides.

"But in the past fortnight, things have taken a sinister turn for the worse, and it has been organised and orchestrated by Yes Scotland, who are organising for mobs to turn up at each meeting to try and intimidate me, which won't work, and to try and silence undecided voters."

Mr Murphy claimed the intimidation is being co-ordinated via social media sites such as Facebook, and by local Yes Scotland offices.

Asked to clarify if he believed the protests were being organised by the official Yes Scotland organisation led by chief executive Blair Jenkins, he said: "This is being co-ordinated by Yes Scotland - how high up it is, I don't know.

"But I now have a view of how broad it is, and it is very broad indeed."

Better Together campaign director Blair McDougall is writing to Mr Jenkins demanding that the Yes campaign "condemn it (intimidating and abusive behaviour) and call it off", Mr Murphy said.

Pressed on whether he accepted that abusive behaviour had already been condemned by Mr Jenkins and other figures in the Yes campaign such as Alex Salmond, Mr Murphy said: "I have no idea - I don't know how high up this goes in the Yes campaign.

"Somewhere inside the Yes campaign, this is being co-ordinated."

He added: "They have turned this tap on, they can turn it off."

A spokesman for Yes Scotland said: 'We condemn all forms of abusive, dangerous and offensive behaviour, whether it be Jim Murphy having eggs thrown at him, or Alex Salmond being harassed by a road rage motorist.

"For the most part, the independence debate has been conducted in a responsible, peaceful and enthusiastic manner with only a very small minority on both sides behaving badly.

"The eyes of the world are on Scotland and it is vital that everybody - regardless of which side of the debate they are on - helps to show off Scotland at its best."

Both the Prime Minister and the First Minister condemned the incident in Kirkcaldy.

Speaking during his visit to Scotland, David Cameron said: ''I think the responsibility for the people doing these things lies with the people doing these things."

Mr Salmond said: ''People shouldn't throw eggs at somebody, full stop, that's something that happens in elections.

''The road rage incident was a very bad example but I don't make that an issue. I don't make the death threats from a few daft people I've had an issue, because I know 99.9% of people in Scotland are enjoying and being energised by a wonderful political debate."