Scottish universities have received at least £28 million in research funding from international arms companies, nuclear bomb manufacturers and government defence agencies.

An investigation has revealed that five leading universities - Strathclyde, Edinburgh, St Andrews, Glasgow and Heriot-Watt - have all taken multi-million pound handouts from BAE Systems, Rolls Royce, the Atomic Weapons Establishment and other defence firms for military research.

The revelation has prompted accusations that academic research has been "polluted" by an unethical killing industry. But this was denied by the universities, who said the research was not directly related to weapons, and could have socially useful spin-offs.

The investigation was carried out by the former Socialist MSP Tommy Sheridan for his social research degree at Strathclyde University. Using freedom of information legislation, he requested details of military research projects from 10 universities since 2000.

He discovered that his own university, Strathclyde, received more military funding that any other in Scotland. Over the last eight years it has received £7.84m for 79 defence-related projects, including 10 funded by BAE Systems, the world's third largest defence company, and nine by the Atomic Weapons Establishment, which maintains and develops Trident nuclear warheads at Aldermaston in Berkshire.

The projects included £170,000 for "management and operation of the Atomic Weapons Establishment", £77,500 from BAE Systems for a "high -power disk laser study", £134,646 from Rolls Royce Naval Marine for "advanced array technology" and £833,986 from the Ministry of Defence for a "high power band width transmitter".

Sheridan also uncovered £5.75m worth of military research on 66 projects at St Andrews University since 2000. The funding came from BAE Systems, the government spin-off defence company Qinetiq, Rolls Royce, Boeing and others, though the university declined to provide details.

Heriot-Watt University in Edinburgh reported £1.73m in military research, more than £1m of which came from BAE Systems for "signalling, navigation, recognition, planning and integration systems". Edinburgh and Glasgow Universities refused to answer questions, but he assembled information from other researchers.

"It is a sad reflection on both society as a whole and the university sector specifically that so much university research now is military related," said Sheridan.

"Every pound invested in researching how to kill and maim other human beings is not only a pound lost to cancer, anti-poverty and renewable energy research, it also represents a waste of publicly-trained scientists, researchers and university laboratory space."

For Sheridan, who leads the Solidarity political party and is now studying for a law degree, said the military funding was "a hidden shame".

He said many universities already avoided links with the tobacco industry. "Money from tobacco companies is not deemed ethically acceptable, so why should money from private military companies, who trade in weapons of death and encourage the dangerous and damaging global arms trade, be acceptable?"

None of the universities disputed Sheridan's figures, though they all rejected his criticisms. .

A spokesman for the University of St Andrews said: "The university is not part of the international arms trade and to suggest this is a gross distortion of the facts."

The University of Strathclyde said it attracted significant amounts of military money because it was home to Scotland's largest engineering faculty.

"The levels of funding reflect the university's reputation for world-class research in areas in which we excel," said deputy principal, professor Allister Ferguson. "Research income is increasing and we will continue to build strategic partnerships with industry, business, government, the research councils and other funding bodies."

Heriot-Watt University stressed that it only undertook work on projects that had civil as well as military uses, such as manufacturing and materials corrosion. Its military research amounted to just 1.7% of its total research funding of £100m.

Military research carried out by the University of Glasgow included wing technology, solar cells for space flight and improved airport security. "All of these will have positive and beneficial applications for the public in the future," said a university spokesman.

A University of Edinburgh spokesperson said: "The university is transparent in its financial dealings and students and staff have the right to raise issues of concern through the appropriate channels."

Sheridan was supported by Scientists for Global Responsibility, which represents 950 engineers and science researchers. It has been investigating the military funding of UK universities for the last five years.

"Our experience is that military involvement in increasingly commercialised universities imports secrecy and a reluctance of researchers, and especially senior staff, to talk about the work," said Dr Chris Langley.

"Many university research groups which work with corporate partners are also supported by public funds, and thus public money is being used to assist the profitability of corporations."

Langley also accused some universities of undertaking research that was "almost entirely" for military purposes.