When the overuse of anti-psychotic drugs to help calm elderly people living in care homes was first exposed, relatives were shocked and politicians called for change.

Targets were quickly set to tackle routine overprescription of such drugs.

But Dr Peter Gordon, a consultant psychiatrist at NHS Forth Valley, thinks we didn't ask a key question: "How did we get there in the first place?"

One way, he suggests, may have been the influence of drug companies. "Some doctors are supported by the pharmaceutical industry. They either call them key thought leaders or opinion leaders and they are paid for speaking fees, flights, hotels and other travel expenses.

"I am not saying the overprescribing of anti-psychotics in the elderly is just down to pharmaceutical promotion, but the fact is that promotion has been enormous."

Dr Gordon is one of a group of doctors, including Ben Goldacre of the Bad Science book and website, and Glasgow GP Dr Margaret McCartney, who are calling for much greater transparency over payments that medical practitioners receive from "big pharma".

He is the author of a public petition currently under consideration at the Scottish Parliament's Petitions Committee, which calls for the passing of a Sunshine Act, which would require doctors to declare all payments and the cash value of gifts in kind on a publicly accessible register.

The US already has a Sunshine Act, while other countries, such as France and Australia, are considering one.

Dr Gordon says there is a perception in the medical profession that doctors are above financial inducement and can resist marketing pressure.

If that is the case, he argues, there should be no problem in being transparent about payments. "I am absolutely not arguing we should outlaw conflicts of interest," he told an evidence session for MSPs on the petitions committee. "I am arguing we should insist on transparency"

Patients should simply know if their doctor is receiving money from a commercial company, and can judge for themselves if there is any conflict, he says.

In the absence of immediate action, the group - who support an open central register on which payments can be recorded - have set up their own. The pilot website www.whopaysthisdoctor.org is inviting doctors to declare any financial links to healthcare and pharmaceutical firms on a voluntary basis.

It mimics the US Dollars for Docs website, but that has the backing of law. Whether people will use a voluntary register is debatable.

A 2003 Health Department letter told health boards they should establish a register of interest for all NHS employees. But although they should, most don't, Dr Gordon found out.

A freedom of information request he submitted to all 22 NHS boards in Scotland last year found none had a completely open-access register on which doctors routinely record interests. Some have a register, but recording is patchy. Many said they simply don't hold the information. Ten years since the Government circular, Dr Gordon describes this as shocking.

"There has been guidance on this since pre-devolution. Doctors and health boards are just not following it. If they do have a policy it is ignored."

He added: "The potential for harm from overprescribing or misprescribing is significant There is no reason why healthcare should be immune from conflicts of interest."

Across the UK, £40 million was paid to healthcare workers by the pharmaceutical industry last year, and an estimated £4m of that came to Scottish healthcare workers.

In Scotland, sponsorship by the pharmaceutical industry is key to the continuing education and training doctors receive once they have qualified, he points out.

The Scottish Government could lead the UK on this issue, he says. "This does not just affect doctors. There are others such as pharmacists, nurse practitioners and academics. But we have to start somewhere," he adds.

Patients are ultimately the losers unless there is full transparency on payments, he says. "We have a system in place for parliament, so we know who pays our MPs. Why don't we have it for our healthcare?"

The General Medical Council (GMC), which is already responsible for maintaining the professional register of doctors, has been suggested as a possible host for the register.

It too already has guidance for doctors on how to deal with potential conflicts of interest.

Responding to the petition's committee, its director of strategy Paul Buckley said: "Our guidance for doctors makes clear they must be open and honest about any financial and commercial interests, and they must not allow these to affect the way they treat or care for patients.

"The guidance also sets out that doctors must be open about any conflict, declaring interests formally, and should be prepared to exclude themselves from decision-making."

Since April 2006 more than 200 doctors have been referred to the GMC due to complaints about conflict of interest, he said. Of those doctors who were referred to panel hearings, five were erased, six suspended and four had conditions put on their licence.

Mr Buckley said the GMC would assess the practicality of keeping a list of doctors' interests attached to their registrations.

The Association of the British Pharmaceutical Industry argues collaboration between healthcare professionals and life science companies has helped drive advances in patient care.

Meanwhile, its Scottish director, Andrew Powrie-Smith, told MSPs members have already agreed to reveal payments to medical professionals from 2016, in line with a European disclosure code.

However those behind whopaysthisdoctor.com say this is no panacea as doctors will be permitted to opt out of having payments declared.

The committee was due to resume consideration of Dr Gordon's petition next week but will now not do so until February 18 to allow for further responses.