THE convener of Holyrood's petitions committee has called for an inquiry into its working practices following claims it has been short-changing the public.

Michael McMahon admitted the number of petitions considered by MSPs has dropped dramatically in recent years.

A recent review failed to explain the drop and, with a more detailed inquiry required, he will call on his successor to investigate the problem fully after next May's election.

The comes after The Herald revealed figures showing hundreds of petition proposals have been thrown out by officials as unsuitable before they were even seen by MSPs on the committee.

Barely a quarter of the requests for action submitted to parliament were considered by the committee.

The figures showed 649 petition proposals were submitted between 2011/12 and 2014/15 but only 170 were presented to MSPs.

The equivalent committee in the Welsh Assembly considered twice as many petitions over the same period.

Labour MSP Mr McMahon promised to review the committee's procedures after he was appointed for a second stint as convener earlier this year.

He previously held the position between 2003 and 2007.

During that time, the work of the committee was recognised in The Herald Scottish Politician of the Year Awards.

He said: "We don't yet have an understand of those petitions which do not get through the system.

"The Herald's story has flagged up an issue and made us think.

"We must ask ourselves: Is there anything we can do to address the concerns of people who do not get their petition through?

"We need to see if there are any structural issues that prevent petitions going through."

He added: "Is there something within the system that could be tweaked?

"The criteria for accepting petitions have not altered and there has been no desire from members of the committee to prevents petitions coming through.

"If there are obstacles that can be removed or reduced then obviously we have a responsibility to try to do that.

"We want to make the system easy for people to use.

"We want to be as open and transparent as we can be."

Between 1999 and 2007, more than a 1000 petitions were put before MSPs.

Since then, the committee has looked into about 600.

The petitions committee was created in 1999 as Holyrood's "doorway to democracy" for members of the public.

People can use petitions - which do not need to be signed by hundreds of people - to request changes in the law or to government policy.

For petitions to be valid, they must meet strict criteria.

They include:

* A petitioner must show they have already tried to resolve the issue in other ways.

* The issue must relate to national, rather than local policy.

* The parliament must have the power to act on the issue.

* Petitions cannot bring up the same issue again until 12 months have passed.

A number of theories have been put forward to explain why large numbers have been ruled invalid in recent years.

It has been suggested members of the public are increasingly turning to Holyrood to resolve issues that are reserved to Westminster.

Officials also noticed that last year saw a surge in petitions relating to issues that would be faced by an independent Scotland. They were ruled invalid.