More than £4m was invested in some of the world's largest arms manufacturers last year by Oxfordshire's local government pension fund.

Information obtained under the Freedom of Information Act shows £4.2m was ploughed into companies manufacturing munitions.

The fact that Oxfordshire County Council, which administers the fund, is supporting the arms trade through the scheme has been described as "repugnant" by Mark Fysh, branch secretary of Oxfordshire trade union Unison.

Investments have been made in companies like BAE Systems, the UK's largest arms company, and US firm Lockheed Martin, the world's largest arms company and manufacturer of nuclear weapons and, according to Human Rights Watch, cluster bomb components.

Mr Fysh said: "Unison understands the need for pension funds to perform well, and the fact that many British jobs are involved in the military.

"However, the idea that I and thousands of other members of the pension scheme here are funding the manufacture of arms sold to blow men, women and children to bits on a monthly basis in the most repressive regimes on earth is repugnant.

"There must be firms on the market that perform as well as BAE and others if we can't use our financial power to change things for the better, then who can?"

Across the south east pension funds for local government employees in Hampshire, East Sussex, Buckinghamshire, Surrey and Kent invested £82m in arms companies, according to information released by the Campaign Against the Arms Trade.

The fact that most of those who pay into pension funds are unaware which companies are being supported has prompted calls for the council to adopt an ethical investment policy.

Green Party South East MEP Caroline Lucas said: "This data puts the lie to the notion councils are only investing in cash-strapped vital UK firms and exposes the sheer scale of local authorities' involvement in the munitions business."

County council spokesman Jane Young said: "The council requires its fund managers to monitor and assess the social, environmental and ethical considerations, which may impact on the reputation of a particular company when selecting and retaining investments, and to engage with companies on these issues where appropriate.

"The council believes the operation of such a policy will ensure the sustainability of a company's earnings and hence its merits as an investment."