Activists advised to steer clear of Protestant march through Edinburgh amid fears of clashes damaging the yes campaign

Scottish republicans have urged leftwing activists to ignore an anti-independence march by the Protestant Orange Order, which takes place five days before the referendum.

The James Connolly Society (JCS), a pro-Irish republican group which supports Scottish independence, has warned its supporters not to stage any protests against the Orange Order parade through central Edinburgh to avoid violent clashes damaging the yes campaign.

Jim Slaven, chairman of the JCS, one of Scotland's largest republican groups, said: "We are asking our members and supporters to concentrate on making the positive case for the break up of the UK state and not to respond to the Orange Order's provocation in coming weeks."

The parade on Saturday 13 September is expected to draw up to 15,000 members of Scottish and Northern Irish Orange Order lodges and flute bands, as well as the Loyalist Apprentice Boys of Derry, in one of the largest but most controversial pro-union rallies of the referendum campaign.

In parallel with Slaven's concerns, leaders of the official pro-UK campaign, Better Together, fear the parade by the militantly unionist order will alienate centre-left and Catholic no voters at a critical time and increase sectarian tensions.

The Orange Order parade comes only a day after Ukip leader Nigel Farage stages a party rally against independence in Glasgow.

Worried about the backlash boosting the yes vote, Better Together has refused to work with either the Orange Order or Ukip because they are regarded as too divisive. With the latest polls showing a narrow six-point gap between yes and no, their rallies in the last week of the campaign will unnerve no campaigners.

Slaven said the decision by City of Edinburgh council to allow the Grand Orange Lodge of Scotland to march was a disgrace, but added that republicans and leftwing groups should protest against the demonstration at a later date through official channels.

"The nature and timing of our opposition will be decided by republicans not by the Orange Order. These marches are a political problem and require a political solution," he said.

Slaven's group is named after the Edinburgh-born Marxist and Irish republican leader James Connolly, who was executed by the British army for taking part in the 1916 Easter rising in Dublin. It backs Scottish independence but opposes the Scottish National party's policies on retaining the Queen as head of state and using sterling.

This year Sam "Skelly" McCrory, the Loyalist commander of the Ulster Defence Association's prisoners in the Maze jail during the last years of the Troubles, had urged Northern Irish loyalists and Orange Order members to stay away from Scotland to avoid damaging the no campaign.

McCrory told the Guardian he feared Northern Irish loyalists would alienate Catholic voters and other centre-left Scots. "The case for the union over here is economic not emotional: it's about jobs, it's about the currency; it's not really about flying flags. Loyalists from Northern Ireland should leave Ulster's politics out of this," he said.