More than £18m has been invested on behalf of MSPs, hundreds of thousands of which has gone into firms which have already been criticised for their close links to the failed African state. The companies involved include Anglo-American, the mining giant which is investing $400m (£208m) to develop a platinum mine in Zimbabwe.

Prime Minister Gordon Brown recently warned the firm that it should think again about "supporting" the Mugabe regime in this way. And Conservative leader David Cameron has called on all companies and individuals with "any dealings" in Zimbabwe to ensure that they are not keeping Mugabe in power.

But figures released by the Scottish Parliament show that MSPs have invested more than £100,000 in Anglo-American via the pension fund. There are also substantial investments in other companies heavily involved in the country, including Standard Chartered bank, Rio Tinto, Barclays and Royal Dutch Shell. On the back of these and other investments, the MSPs' fund grew by £700,000 last year.

The revelations come weeks after several MSPs backed the decision to strip Mugabe of his knighthood and called on the international community to redouble their efforts to bring about change in the country.

Last night, one senior MSP on the Scottish Parliament Corporate Body (SPCB) – its ruling council – said the revelation was "regrettable" and he would examine whether it was possible to switch the money.

Mike Pringle said: "It is extremely regrettable that the Scottish Parliament has to be involved in investing in Zimbabwe. I would be hopeful that as a Corporate Body we would be able to influence this decision.

"As a member of the Corporate Body I will be suggesting that they discuss this with Baillie Gifford (their investment managers] to find out whether there is any flexibility in the way it is managed."

Senior Nationalist MSP Roseanna Cunningham said: "I have no idea how it's funded or invested in that sense but, like most MSPs, I would be pretty concerned."

The MSPs' scheme requires them to pay in 6% of their £54,000 salary each year. In return they get back a generous one-50th of their final salary for each year at Holyrood.

Adam Ramsay, Ethical Investment campaigner and president of Edinburgh University Students' Association, said: "By investing in a company, the Scottish Parliament is giving both financial and moral support to what the company is doing. You can't condemn something with one hand if you are paying for it with the other."

Along with Anglo-American, Barclays has attracted the greatest controversy for its Zimbabwean operations. It owns two-thirds of Barclays Bank Zimbabwe, and contributes to a government loan scheme that is thought to have lent money to at least five ministers for farm improvements. Standard Chartered operates in a similar manner. Rio Tinto, another mining giant, has a diamond mine at Murowa.

A spokeswoman for the Scottish Parliament said: "The Members' Pension Scheme is part of a pooled fund... which operates in accordance with the United Nation's Principles for Responsible Investment.

"Our total investment in this fund would have to be worth more than £50m in order for MSPs to be able to direct the investments."

Anglo-American claimed last night that withdrawing investment from its activities in Zimbabwe would only make things worse in the ravaged country.

"Anglo-American is deeply concerned about the current political situation in Zimbabwe and condemns the violence and human rights abuses that are taking place," it said. "The responsible development of the Unki mine will create a long-term viable business which will be important to the economic future of Zimbabwe for years to come."

Another Nationalist MSP, Bill Wilson, has written to Zimbabwean opposition leader Morgan Tsvangirai expressing his concern that "such investments might be serving to perpetuate Robert Mugabe's despotic regime".

The Parliament's Fund has previously attracted controversy after it emerged it also invested in British America Tobacco – despite having voted through a ban on smoking in public places.

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