MSPS are to consider whether they should be banned from holding paid directorships or consultancies.

Presiding Officer Tricia Marwick mounted a robust defence of Holyrood rules covering outside work following a call by Scottish Labour leader Jim Murphy for stricter limits to be imposed.

However she has asked the parliament's standards committee to consider a possible review.

Mr Murphy has pledged to ban MSPs from holding paid directorships or consultancies if Labour win next year's Holyrood election.

In a recent letter to the Presiding Officer, he said he believed the Scottish Parliament was "above reproach".

But he added: "The Scottish people need to know that when they vote they are electing an individual who will represent them directly, and not be swayed by private interests."

In her reply, made public yesterday, Ms Marwick said the parliament placed "stronger checks and balances on our members than exist elsewhere".

But she said: "There is always merit in reviewing our rules with a critical eye."

Stewart Stevenson, the SNP former minister who chairs the standards committee, said: "Any correspondence we receive we take seriously and we will look at this at our next meeting in a fortnight's time."

The news that former foreign secretaries Malcolm Rifkind and Jack Straw were secretly filmed offering their services to a bogus Hong Kong company, during a newspaper investigation, sparked fresh anger at MPs' outside employment this week.

Sir Malcolm stepped down as chairman of the Commons Intelligence and Security Committee and announced he would also stand down as an MP following an outcry over the revelations.

A much higher proportion of MPs than MSPs take outside work, which is permitted by both parliaments.

However Ms Marwick said it was a criminal offence for MSPs, unlike for MPs, to fail to register or declare significant financial interests.

MSPs could also face criminal charges if they engaged in "paid advocacy" or lobbying.

Ms Marwick said no MSPs held consultancies and the number who were company directors was "in single figures".

She added: "Of the very limited number of MSPs that hold a second paid role, the majority receive small amounts of income for a limited amount of their time."