The mother of a British student who died mysteriously in Germany five years ago is taking a petition to Downing Street to ask for help investigating her son's death.

Jeremiah Duggan, 22, from Golders Green, was found dead on a motorway in Wiesbaden, Germany, on March 27, 2003, after attending an antiwar protest run by the Schiller Institute.

German police decided that the student had committed suicide by running into the road, but doubts have since been cast on this verdict.

Six weeks ago the British Attorney General refused Erica Duggan's request to open a second inquest into the death, prompting her to make the trip to Number 10.

Accompanied by Rudi Vis, Labour MP for Finchley and Golders Green, Mrs Duggan will present her petition to Gordon Brown next Thursday, along with a personal letter outlining her concerns.

She said: "What I am doing is putting the truth out in the public domain. I am saying that I'm doing everything I can possibly do to find out what happened to my son.

"The Attorney General refused our application behind closed doors, without supplying us with any of the documents we requested from the coroner or German authorities. I am absolutely shocked. It is the end fo the road of betrayal.

"I want Gordon Brown to convince the German authorities to open a genuine inquiry in Germany, or to get the British police involved to gather the evidence needed. He has the power to do that."

Mr Duggan was studying at the Sorbonne in Paris when he decided to travel to Wiesbaden for the antiwar protest. Accompanying him was a group of young men led by Lyndon LaRouche, an American rightwing extremist and former presidential candidate who has been condemned by leading Jewish organisations as an anti-semite.

Mr Duggan's family say the student knew nothing of the group's background until he heard anti-semitic comments being made at the conference. They believe strongly that he died as a result of his involvement with LaRouche, citing as evidence a phonecall he made 45 minutes before he was killed, when he "sounded terrified" and said he was "in deep trouble".

Throughout the controversy, the Schiller Institute has denied any involvement in his death. However, the German view that Mr Duggan committed suicide was rejected by a British inquest in 2003, and in 2007 three leading forensic experts confirmed this opinion.

Last year 76 cross-party MPs signed an early day motion calling on ministers to reopen British and German inquiries, but without success.

Mr Vis said he decided to help Mrs Duggan because his "honest opinion was that her son was murdered".

He added: "There is ample evidence that she is putting in her letter to Gordon Brown that not enough attention has been given to this case.

"We are getting somewhere, but slowly. We will have to keep on pressing."

A spokesman for the Foreign Office said that the Government's hands were tied in the matter because "it could not interfere with the legal system of another country", but Mrs Duggan said that she would not stop until she had achieved justice for her son.

"Whether Gordon Brown gives me justice or not, this campaign will go on. We are going to continue collecting signatures not just from this country, but from around the world.

"What I am doing on Thursday is saying: look at what I have done and help me."