Janitors in schools across Scotland's biggest city have begun a five-day strike.

The industrial action is taking place across Glasgow's primary and additional support schools, as well as nurseries, from Monday.

The strike marks an escalation in the janitors' dispute with Cordia, an arm's-length body of Glasgow City Council.

Unison, the janitors' union, says Cordia and the council are refusing to talk amid the dispute which has been ongoing since January.

The janitors began a five-day strike on Monday. They also plan to stage a protest outside Glasgow City Chambers on Monday at 12.30pm.

They also plan to seek the support of Glasgow's new MSPs when they hold a lunchtime demo outside Holyrood on Wednesday.

Last month, Cordia said there was "no possibility of a settlement".

Sam Macartney, Unison branch officer, said: "Our jannies deserve justice. Glasgow City Council is treating them with contempt.

"We will be asking Glasgow's newly elected MSPs to support the Justice4Jannies campaign"

A spokesman for Cordia said: "Around a third of the organisation's janitors are taking part in industrial action this week. Allegations circulating that the organisation is spending £3000 per day to cover duties are absurd.

"Cordia is utilising suitably trained employees to carry out janitorial tasks and all staff members contributing to contingency arrangements are paid the normal janitorial rate for any hours they work out of their working patterns."

Last month the firm said: "Cordia has been through an extensive formal grievance process with the janitorial staff who are participating in industrial action.

"The issue has been subject to the Collective Disputes procedure, giving Unison three opportunities to outline their issues.

"The final decision by the nominations, appointments and appeals sub-committee rejected Unison's claim for a Working Context and Demands Payment for Janitors.

"As additional context, Janitors were assessed as part of the Work, Pay and Benefits Review in 2006 with no significant change in their duties since that time.

"Cordia has completely exhausted all internal processes after negotiations with Unison and is not required to convene a meeting to further negotiate when at this stage, there is no possibility of a settlement."

The strikers have the support of the Scottish Trade Union Congress (STUC) and shadow chancellor John McDonnell MP.

Unison estimates Cordia is spending £3000 each day in an attempt to cover the janitors' duties and break the industrial action.

The janitors have taken nine days of industrial action since mid-March. More strikes are planned and Unison members employed by Cordia as school janitors began industrial action on January 19 by boycotting a number of duties

Cordia is refusing to pay a Working Context and Demands Payment (WCD) to school janitors and is using "spurious" arguments to justify not making this payment, Unison says.