NICOLA Sturgeon is to toughen the ministerial code of conduct for the second time in four months after MSPs demanded greater transparency around the work of ministerial aides.

The First Minister bowed to pressure from Holyrood’s standards committee to reform the rules on parliamentary liaison officers (PLOs), who act as the eyes and ears of ministers.

The Herald revealed earlier this year that Ms Sturgeon had appointed PLOs to the committees which were also supposed to scrutinise their cabinet secretaries.

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Jenny Gilruth, PLO to Education Secretary John Swinney, was put on the education committee, while Kate Forbes, PLO to Finance Secretary Derek Mackay, was put on the finance committee - a pattern that repeated across every Cabinet brief.

After claims of conflicts of interests, Ms Sturgeon later removed PLOs from the committees most closely associated with their bosses.

She also revised the Ministerial Code in August to ensure PLOs declared their role “the first time” they took part in parliamentary business related to their cabinet secretary.

However the standards committee said this was not enough, and that PLOs should declare their status “on each occasion” which is relevant, not merely the first in a Holyrood term.

The First Minister has now replied to the committee agreeing to the change.

She wrote: “I believe it is essential that the public has full confidence in this Parliament and its ability to hold the Government of the day to account.

“Therefore, I am always willing to consider ways in which we can enhance the transparency of Parliamentary business.

“For those PLOs attached to my own office, this new obligation means that they should make such declarations when they are engaging with me directly in Parliament, for example at FMQs, in any parliamentary statement or debate when I am leading or when I appear before a Committee on which one of them sits.”

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At Westminster, the equivalent of PLOs, Parliamentary Private Secretaries, are banned from sitting on committees scrutinising their ministers.

The same rule also applied in Scotland until 2007, but was quietly dropped by Alex Salmond when the SNP first came to power.