THE SNP have called on Douglas Ross to speak out after the latest claims Boris Johnson has broken the ministerial code.

A copy of the Conservative party’s spending return revealed the alleged breach by the Prime Minister, who is accused of using taxpayers' cash to campaign in the Hartlepool by-election.

The Tories ultimately won the election on May 6 this year, with candidate Jill Mortimer taking up a seat in the House of Commons.

The SNP have said that Johnson will try to “sweep this under the carpet as usual” but that “serious questions” need to be asked over the ministerial breach.

READ MORE: Douglas Ross stays silent after Boris Johnson 'breaks ministerial code'

They also called on Ross to speak out as he has previously been “keen to ensure others upheld the Ministerial Code in the past”.

Ross repeatedly claimed Nicola Sturgeon should resign over claims she had broken the ministerial code, but remained silent on ministerial code breaches alleged by Tory UK Government ministers.

He has even described ministerial code breaches as “straight red, even in the most lenient referee’s book”.

Kirsten Oswald MP, SNP Westminster Depute Leader, said: "The stench of cronyism and sleaze surrounding this Tory government grows stronger with each day that passes.

The National:

Kirsten Oswald called on Douglas Ross to make a statement after the breach claims came to light

"Boris Johnson will try his best to sweep this under the carpet as usual, but serious questions must be asked over whether or not he and his ministerial colleagues have, yet again, broken the Ministerial Code.

"Seeing as Douglas Ross was so keen to ensure others upheld the Ministerial Code in the past, he will no doubt speak out on this without delay.

"It is clear that the Westminster system is rotten to the core and broken beyond repair. Scotland can, and must, shake off the Westminster system in order to build a fairer and more democratic future as an independent nation."

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We told how a report by the Insider revealed Johnson flew to Teeside International Airport, near Middlesbrough, on April 1.

Initially, the Prime Minister conducted official government business at a local B&Q in Middlesbrough, before being taken by motorcade to Hartlepool to meet with Mortimer.

They visited a local company before heading to a nearby housing estate to leaflet, doorknock and speak to residents.

However, none of these costs were included on the spending return, which clearly states that the candidate spent nothing on transport.

The National:

Johnson campaigned with Mortimer in Hartlepool on more than one occasion

The Ministerial Code clearly states that ministers must not use government resources for "party political purposes” and when the visit is a mix of political and official engagements, “it is important that the department and the Party each meet a proper portion of the actual cost”.

A spokesperson for the Tories told the Insider that the costs were declared under "Staff costs" in the spending return, but reportedly would not provide evidence of this.

The Scottish Conservatives have been contacted for comment.